Add errcheck & misspell to golangci and fix their issues

Signed-off-by: sazary <soroosh@azary.ir>

.golangci.yml

@@ -12,12 +12,20 @@ linters:
     - gofumpt
     - goimports
     - revive
+    - misspell
+    - errcheck
   disable-all: true
 
 issues:
   max-same-issues: 0
+  exclude-rules:
+    - path: _test.go
+      linters:
+        - errcheck
 
 linters-settings:
+  errcheck:
+    exclude: scripts/errcheck_excludes.txt
   goimports:
     local-prefixes: github.com/prometheus/client_golang
   gofumpt:

prometheus/push/push.go

@@ -273,7 +273,11 @@ func (p *Pusher) push(ctx context.Context, method string) error {
 				}
 			}
 		}
-		enc.Encode(mf)
+		if err := enc.Encode(mf); err != nil {
+			return fmt.Errorf(
+				"failed to encode metric familty %s, error is %w",
+				mf.GetName(), err)
+		}
 	}
 	req, err := http.NewRequestWithContext(ctx, method, p.fullURL(), buf)
 	if err != nil {

prometheus/testutil/testutil.go

@@ -101,7 +101,9 @@ func ToFloat64(c prometheus.Collector) float64 {
 	}
 
 	pb := &dto.Metric{}
-	m.Write(pb)
+	if err := m.Write(pb); err != nil {
+		panic(fmt.Errorf("error happened while collecting metrics: %w", err))
+	}
 	if pb.Gauge != nil {
 		return pb.Gauge.GetValue()
 	}

scripts/errcheck_excludes.txt

@@ -0,0 +1,5 @@
+// The following 2 methods always return nil as the error
+(*github.com/cespare/xxhash/v2.Digest).Write
+(*github.com/cespare/xxhash/v2.Digest).WriteString
+
+(*bufio.Writer).WriteRune