feat: Add Go SDK custom header support and README (#1288)

Following our node sdk's design, allow developers to set custom headers on Go SDK requests. Request specific custom headers will override headers defined in the sdk's settings/config. This will allow the Go SDK caller to set Accept headers and other custom headers. Also add README for Go SDK.

Also fixes issue stated in #1075. (Not the main one, but other one brought up by Go SDK users)

go/README.md

@@ -0,0 +1,118 @@
+# Go Looker SDK
+
+The Go Looker SDK provides a convenient way to call your Looker instance's [Looker API](https://developers.looker.com/api/overview). The Go Looker SDK supports at least Go version 1.17.6 and 1.16.13 (subject to change). This SDK is community supported with contributions and discussion from the Looker developer community. We strive for functional parity with our original javascript/typescript SDK. Thanks for using our Go Looker SDK!
+
+## Basic Usage
+
+Example code snippet below for basic SDK setup and usage. Also `git clone` this sdk-codegen repo and run the [example code](go/example/main.go). 
+
+```go
+import (
+    "fmt"
+    "github.com/looker-open-source/sdk-codegen/go/rtl"
+    v4 "github.com/looker-open-source/sdk-codegen/go/sdk/v4"
+)
+
+func main() {
+    // Get settings from either looker.ini file OR environment:
+    // looker.ini file
+    cfg, err := rtl.NewSettingsFromFile("path/to/looker.ini", nil)
+    // environment
+    cfg, err := rtl.NewSettingsFromEnv()
+
+    // Create new auth session with sdk settings. 
+    // The auth session will fetch/refresh the access 
+    // token from your Looker instance's `login` endpoint. 
+    session := rtl.NewAuthSession(cfg)
+
+    // Create new instance of the Go Looker SDK 
+    sdk := v4.NewLookerSDK(session)
+
+    // Call the Looker API e.g. get your user's name
+    me, err := sdk.Me("", nil)
+    fmt.Printf("Your name is %s %s\n", *(me.first), *(me.last))
+}
+```
+
+## Advanced usage
+
+### Custom headers
+
+You can set custom headers on Looker Go SDK's requests. They can either be applied to all outgoing requests or per outgoing request. 
+
+#### Custom headers for all requests
+
+Follow the example code snippet below if you want all outgoing requests to have the same custom headers.
+
+```go
+func main() {
+    cfg, err := rtl.NewSettingsFromFile("path/to/looker.ini", nil)
+
+    // Set the Headers option in the settings/config
+    cfg.Headers = map[string]string{
+        "HeaderName1": "HeaderValue1",
+        "HeaderName2": "HeaderValue2",
+    }
+
+    session := rtl.NewAuthSession(cfg)
+    sdk := v4.NewLookerSDK(session)
+}
+```
+
+#### Custom headers per request
+
+Follow the example code snippet below if you want each outgoing request to have different custom headers. **These headers will overwrite any custom headers set in the SDK's settings as outlined in the previous [All Requests section](#custom-headers-for-all-requests).**
+
+```go
+func main() {
+    cfg, err := rtl.NewSettingsFromFile("path/to/looker.ini", nil)
+    session := rtl.NewAuthSession(cfg)
+    sdk := v4.NewLookerSDK(session)
+
+    // Set the headers in the options passed into the SDK method
+    sdk.Me("", &ApiSettings{Headings: map[string]string{
+        "HeaderName1": "HeaderValue1",
+        "HeaderName2": "HeaderValue2",
+    }})
+}
+```
+
+### Timeout 
+
+You can set a custom timeout (in seconds) on Looker Go SDK's requests. The timeout defaults to 120 seconds. A timeout can either be applied to all outgoing requests or per outgoing request. 
+
+#### Timeout for all requests
+
+Set `timeout` in your sdk's looker.ini file then call `NewSettingsFromFile()`.  
+```YAML
+[Looker]
+timeout=60
+```
+
+OR
+
+Set `LOOKERSDK_TIMEOUT` environment variable then call `NewSettingsFromEnv()`.
+```bash
+LOOKERSDK_TIMEOUT=60
+```
+
+#### Timeout per request
+
+Follow the example code snippet below if you want each outgoing request to have a different timeout. **The timeout will overwrite the timeout set in the SDK's settings as outlined in the previous [All Requests section](#timeout-for-all-requests).**
+
+```go
+import "context"
+
+func main() {
+    cfg, err := rtl.NewSettingsFromFile("path/to/looker.ini", nil)
+    session := rtl.NewAuthSession(cfg)
+    sdk := v4.NewLookerSDK(session)
+
+    // Set the timeout in the options passed into the SDK method
+    me, err := sdk.Me("", &ApiSettings{Timeout: 60})
+
+    if errors.Is(err, context.DeadlineExceeded) {
+        // Timeout exceeded
+    }
+}
+```

go/rtl/auth.go

@@ -142,7 +142,7 @@ func (s *AuthSession) Do(result interface{}, method, ver, path string, reqPars m
 	}
 
 	// set headers
-	req.Header.Add("Content-Type", contentTypeHeader)
+	req.Header.Set("Content-Type", contentTypeHeader)
 
 	if s.Config.AgentTag != "" {
 		req.Header.Set("User-Agent", s.Config.AgentTag)
@@ -151,6 +151,17 @@ func (s *AuthSession) Do(result interface{}, method, ver, path string, reqPars m
 		req.Header.Set("User-Agent", options.AgentTag)
 	}
 
+	if s.Config.Headers != nil {
+		for key, value := range s.Config.Headers {
+			req.Header.Set(key, value)
+		}
+	}
+	if options != nil && options.Headers != nil {
+		for key, value := range options.Headers {
+			req.Header.Set(key, value)
+		}
+	}
+
 	// set query params
 	setQuery(req.URL, reqPars)
 

go/rtl/auth_test.go

@@ -125,70 +125,6 @@ func TestAuthSession_Do_Authorization(t *testing.T) {
 	})
 }
 
-func TestAuthSession_Do_UserAgent(t *testing.T) {
-	const path = "/someMethod"
-	const apiVersion = "/4.0"
-
-	t.Run("Do() sets User-Agent header with AuthSession config's AgentTag", func(t *testing.T) {
-		mux := http.NewServeMux()
-		setupApi40Login(mux, foreverValidTestToken, http.StatusOK)
-		server := httptest.NewServer(mux)
-		defer server.Close()
-
-		mux.HandleFunc("/api"+apiVersion+path, func(w http.ResponseWriter, r *http.Request) {
-			userAgentHeader := r.Header.Get("User-Agent")
-			expectedHeader := "some-agent-tag"
-			if userAgentHeader != expectedHeader {
-				t.Errorf("User-Agent header not correct. got=%v want=%v", userAgentHeader, expectedHeader)
-			}
-		})
-
-		session := NewAuthSession(ApiSettings{
-			BaseUrl:    server.URL,
-			ApiVersion: apiVersion,
-			AgentTag:   "some-agent-tag",
-		})
-
-		var r string
-		err := session.Do(&r, "GET", apiVersion, path, nil, nil, nil)
-
-		if err != nil {
-			t.Errorf("Do() call failed: %v", err)
-		}
-	})
-
-	t.Run("Do() sets User-Agent header with Do's option's AgentTag, which will overwrite  AuthSession config", func(t *testing.T) {
-		mux := http.NewServeMux()
-		setupApi40Login(mux, foreverValidTestToken, http.StatusOK)
-		server := httptest.NewServer(mux)
-		defer server.Close()
-
-		mux.HandleFunc("/api"+apiVersion+path, func(w http.ResponseWriter, r *http.Request) {
-			userAgentHeader := r.Header.Get("User-Agent")
-			expectedHeader := "new-agent-tag"
-			if userAgentHeader != expectedHeader {
-				t.Errorf("User-Agent header not correct. got=%v want=%v", userAgentHeader, expectedHeader)
-			}
-		})
-
-		session := NewAuthSession(ApiSettings{
-			BaseUrl:    server.URL,
-			ApiVersion: apiVersion,
-			AgentTag:   "some-agent-tag",
-		})
-
-		var r string
-		options := ApiSettings{
-			AgentTag:   "new-agent-tag",
-		}
-		err := session.Do(&r, "GET", apiVersion, path, nil, nil, &options)
-
-		if err != nil {
-			t.Errorf("Do() call failed: %v", err)
-		}
-	})
-}
-
 func TestAuthSession_Do_Parse(t *testing.T) {
 	type stringStruct struct {
 		Field *string `json:"field"`
@@ -454,10 +390,75 @@ func TestAuthSession_Do_Parse(t *testing.T) {
 	})
 }
 
-func TestAuthSession_Do_Content_Type(t *testing.T) {
+func TestAuthSession_Do_Headers(t *testing.T) {
 	const path = "/someMethod"
 	const apiVersion = "/4.0"
 
+	t.Run("Do() sets custom headers if Headers is set in the AuthSession's api settings", func(t *testing.T) {
+		mux := http.NewServeMux()
+		setupApi40Login(mux, foreverValidTestToken, http.StatusOK)
+		server := httptest.NewServer(mux)
+		defer server.Close()
+
+		mux.HandleFunc("/api"+apiVersion+path, func(w http.ResponseWriter, r *http.Request) {
+			headerValue1 := r.Header.Get("Key1")
+			headerValue2 := r.Header.Get("Key2")
+
+			expectedHeaderValue1 := "Value1"
+			expectedHeaderValue2 := "Value2"
+			if headerValue1 != expectedHeaderValue1 || headerValue2 != expectedHeaderValue2 {
+				t.Errorf("Custom headers not set correctly. got=%v and %v  want=%v and %v", headerValue1, headerValue2, expectedHeaderValue1, expectedHeaderValue2)
+			}
+		})
+
+		s := NewAuthSession(ApiSettings{
+			BaseUrl:    server.URL,
+			ApiVersion: apiVersion,
+			Headers: map[string]string{"Key1":"Value1","Key2":"Value2"},
+		})
+
+		var r string
+		err := s.Do(&r, "GET", apiVersion, path, nil, nil, nil)
+
+		if err != nil {
+			t.Errorf("Do() call failed: %v", err)
+		}
+	})
+
+	t.Run("Do()'s options.Headers will overwrite the Headers in the AuthSession's api settings", func(t *testing.T) {
+		mux := http.NewServeMux()
+		setupApi40Login(mux, foreverValidTestToken, http.StatusOK)
+		server := httptest.NewServer(mux)
+		defer server.Close()
+
+		mux.HandleFunc("/api"+apiVersion+path, func(w http.ResponseWriter, r *http.Request) {
+			headerValue1 := r.Header.Get("Key1")
+			headerValue2 := r.Header.Get("Key2")
+
+			expectedHeaderValue1 := "Value1"
+			expectedHeaderValue2 := "OverwriteValue2"
+			if headerValue1 != expectedHeaderValue1 || headerValue2 != expectedHeaderValue2 {
+				t.Errorf("Custom headers not set correctly. got=%v and %v  want=%v and %v", headerValue1, headerValue2, expectedHeaderValue1, expectedHeaderValue2)
+			}
+		})
+
+		s := NewAuthSession(ApiSettings{
+			BaseUrl:    server.URL,
+			ApiVersion: apiVersion,
+			Headers: map[string]string{"Key1":"Value1","Key2":"Value2"},
+		})
+
+		options := ApiSettings{
+			Headers: map[string]string{"Key1":"Value1","Key2":"OverwriteValue2"},
+		}
+		var r string
+		err := s.Do(&r, "GET", apiVersion, path, nil, nil, &options)
+
+		if err != nil {
+			t.Errorf("Do() call failed: %v", err)
+		}
+	})
+
 	t.Run("Do() sets Content-Type header to 'application/json' if body is json", func(t *testing.T) {
 		mux := http.NewServeMux()
 		setupApi40Login(mux, foreverValidTestToken, http.StatusOK)
@@ -517,6 +518,65 @@ func TestAuthSession_Do_Content_Type(t *testing.T) {
 			t.Errorf("Do() call failed: %v", err)
 		}
 	})
+
+	t.Run("Do() sets User-Agent header with AuthSession config's AgentTag", func(t *testing.T) {
+		mux := http.NewServeMux()
+		setupApi40Login(mux, foreverValidTestToken, http.StatusOK)
+		server := httptest.NewServer(mux)
+		defer server.Close()
+
+		mux.HandleFunc("/api"+apiVersion+path, func(w http.ResponseWriter, r *http.Request) {
+			userAgentHeader := r.Header.Get("User-Agent")
+			expectedHeader := "some-agent-tag"
+			if userAgentHeader != expectedHeader {
+				t.Errorf("User-Agent header not correct. got=%v want=%v", userAgentHeader, expectedHeader)
+			}
+		})
+
+		session := NewAuthSession(ApiSettings{
+			BaseUrl:    server.URL,
+			ApiVersion: apiVersion,
+			AgentTag:   "some-agent-tag",
+		})
+
+		var r string
+		err := session.Do(&r, "GET", apiVersion, path, nil, nil, nil)
+
+		if err != nil {
+			t.Errorf("Do() call failed: %v", err)
+		}
+	})
+
+	t.Run("Do() sets User-Agent header with Do's option's AgentTag, which will overwrite  AuthSession config", func(t *testing.T) {
+		mux := http.NewServeMux()
+		setupApi40Login(mux, foreverValidTestToken, http.StatusOK)
+		server := httptest.NewServer(mux)
+		defer server.Close()
+
+		mux.HandleFunc("/api"+apiVersion+path, func(w http.ResponseWriter, r *http.Request) {
+			userAgentHeader := r.Header.Get("User-Agent")
+			expectedHeader := "new-agent-tag"
+			if userAgentHeader != expectedHeader {
+				t.Errorf("User-Agent header not correct. got=%v want=%v", userAgentHeader, expectedHeader)
+			}
+		})
+
+		session := NewAuthSession(ApiSettings{
+			BaseUrl:    server.URL,
+			ApiVersion: apiVersion,
+			AgentTag:   "some-agent-tag",
+		})
+
+		var r string
+		options := ApiSettings{
+			AgentTag:   "new-agent-tag",
+		}
+		err := session.Do(&r, "GET", apiVersion, path, nil, nil, &options)
+
+		if err != nil {
+			t.Errorf("Do() call failed: %v", err)
+		}
+	})
 }
 
 func TestAuthSession_Do_Timeout(t *testing.T) {

go/rtl/settings.go

@@ -19,6 +19,7 @@ type ApiSettings struct {
 	ClientId     string `ini:"client_id"`
 	ClientSecret string `ini:"client_secret"`
 	ApiVersion   string `ini:"api_version"`
+	Headers      map[string]string
 }
 
 var defaultSettings ApiSettings = ApiSettings{