stack: add support for Go 1.13beta1

It now prints 'pc' in addition to 'fp' and 'sp'.

Include unit test.

stack/context.go

@@ -118,7 +118,7 @@ var (
 	//   when a signal is not correctly handled. It is printed with m.throwing>0.
 	//   These are discarded.
 	// - For cgo, the source file may be "??".
-	reFile = regexp.MustCompile("^(?:\t| +)(\\?\\?|\\<autogenerated\\>|.+\\.(?:c|go|s))\\:(\\d+)(?:| \\+0x[0-9a-f]+)(?:| fp=0x[0-9a-f]+ sp=0x[0-9a-f]+)$")
+	reFile = regexp.MustCompile("^(?:\t| +)(\\?\\?|\\<autogenerated\\>|.+\\.(?:c|go|s))\\:(\\d+)(?:| \\+0x[0-9a-f]+)(?:| fp=0x[0-9a-f]+ sp=0x[0-9a-f]+(?:| pc=0x[0-9a-f]+))$")
 	// Sadly, it doesn't note the goroutine number so we could cascade them per
 	// parenthood.
 	reCreated = regexp.MustCompile("^created by (.+)$")

stack/context_test.go

@@ -216,6 +216,42 @@ func TestParseDumpAsm(t *testing.T) {
 	compareString(t, "panic: reflect.Set: value of type\n\n", extra.String())
 }
 
+func TestParseDumpAsmGo1dot13(t *testing.T) {
+	data := []string{
+		"panic: reflect.Set: value of type",
+		"",
+		"goroutine 16 [garbage collection]:",
+		"runtime.switchtoM()",
+		"\t/goroot/src/runtime/asm_amd64.s:198 fp=0xc20cfb80d8 sp=0xc20cfb80d0 pc=0x5007be",
+		"",
+	}
+	extra := &bytes.Buffer{}
+	c, err := ParseDump(bytes.NewBufferString(strings.Join(data, "\n")), extra, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	expected := []*Goroutine{
+		{
+			Signature: Signature{
+				State: "garbage collection",
+				Stack: Stack{
+					Calls: []Call{
+						{
+							SrcPath: "/goroot/src/runtime/asm_amd64.s",
+							Line:    198,
+							Func:    Func{Raw: "runtime.switchtoM"},
+						},
+					},
+				},
+			},
+			ID:    16,
+			First: true,
+		},
+	}
+	compareGoroutines(t, expected, c.Goroutines)
+	compareString(t, "panic: reflect.Set: value of type\n\n", extra.String())
+}
+
 func TestParseDumpLineErr(t *testing.T) {
 	data := []string{
 		"panic: reflect.Set: value of type",