chore: use lowercase in error messages (GoogleCloudPlatform#974)

See https://google.github.io/styleguide/go/decisions.html#error-strings.

Author: enocom

e2e_postgres_test.go

@@ -456,7 +456,7 @@ func TestPostgresSANBadDomainCausesConnectError(t *testing.T) {
 	if err == nil {
 		t.Fatal("Want error, got invalid error")
 	}
-	if !strings.Contains(fmt.Sprint(err), "Dial error: handshake failed") {
+	if !strings.Contains(fmt.Sprint(err), "dial error: handshake failed") {
 		t.Fatal("Want error 'Dial error: handshake failed'.  got: ", err)
 	}
 	t.Log(now)

errtype/errors.go

@@ -30,7 +30,7 @@ func (e *genericError) Error() string {
 // NewConfigError initializes a ConfigError.
 func NewConfigError(msg, cn string) *ConfigError {
 	return &ConfigError{
-		genericError: &genericError{Message: "Config error: " + msg, ConnName: cn},
+		genericError: &genericError{Message: "config error: " + msg, ConnName: cn},
 	}
 }
 
@@ -61,9 +61,9 @@ type RefreshError struct {
 
 func (e *RefreshError) Error() string {
 	if e.Err == nil {
-		return fmt.Sprintf("Refresh error: %v", e.genericError)
+		return fmt.Sprintf("refresh error: %v", e.genericError)
 	}
-	return fmt.Sprintf("Refresh error: %v: %v", e.genericError, e.Err)
+	return fmt.Sprintf("refresh error: %v: %v", e.genericError, e.Err)
 }
 
 func (e *RefreshError) Unwrap() error { return e.Err }
@@ -88,9 +88,9 @@ type DialError struct {
 
 func (e *DialError) Error() string {
 	if e.Err == nil {
-		return fmt.Sprintf("Dial error: %v", e.genericError)
+		return fmt.Sprintf("dial error: %v", e.genericError)
 	}
-	return fmt.Sprintf("Dial error: %v: %v", e.genericError, e.Err)
+	return fmt.Sprintf("dial error: %v: %v", e.genericError, e.Err)
 }
 
 func (e *DialError) Unwrap() error { return e.Err }

errtype/errors_test.go

@@ -30,17 +30,17 @@ func TestErrorFormatting(t *testing.T) {
 		{
 			desc: "config error message",
 			err:  errtype.NewConfigError("error message", "proj:reg:inst"),
-			want: "Config error: error message (connection name = \"proj:reg:inst\")",
+			want: "config error: error message (connection name = \"proj:reg:inst\")",
 		},
 		{
 			desc: "refresh error message without internal error",
 			err:  errtype.NewRefreshError("error message", "proj:reg:inst", nil),
-			want: "Refresh error: error message (connection name = \"proj:reg:inst\")",
+			want: "refresh error: error message (connection name = \"proj:reg:inst\")",
 		},
 		{
 			desc: "refresh error message with internal error",
 			err:  errtype.NewRefreshError("error message", "proj:reg:inst", errors.New("inner-error")),
-			want: "Refresh error: error message (connection name = \"proj:reg:inst\"): inner-error",
+			want: "refresh error: error message (connection name = \"proj:reg:inst\"): inner-error",
 		},
 		{
 			desc: "Dial error without inner error",
@@ -49,7 +49,7 @@ func TestErrorFormatting(t *testing.T) {
 				"proj:reg:inst",
 				nil, // no error here
 			),
-			want: "Dial error: message (connection name = \"proj:reg:inst\")",
+			want: "dial error: message (connection name = \"proj:reg:inst\")",
 		},
 		{
 			desc: "Dial error with inner error",
@@ -58,7 +58,7 @@ func TestErrorFormatting(t *testing.T) {
 				"proj:reg:inst",
 				errors.New("inner-error"),
 			),
-			want: "Dial error: message (connection name = \"proj:reg:inst\"): inner-error",
+			want: "dial error: message (connection name = \"proj:reg:inst\"): inner-error",
 		},
 	}