Modify comment syntax error (#2572)

tools/goctl/api/cmd.go

@@ -16,7 +16,7 @@ import (
 )
 
 var (
-	// Cmd describes a api command.
+	// Cmd describes an api command.
 	Cmd = &cobra.Command{
 		Use:   "api",
 		Short: "Generate api related files",

tools/goctl/api/spec/name.go

@@ -75,7 +75,7 @@ func (t PointerType) Documents() []string {
 	return nil
 }
 
-// Name returns a interface string, Its fixed value is interface{}
+// Name returns an interface string, Its fixed value is interface{}
 func (t InterfaceType) Name() string {
 	return t.RawName
 }

tools/goctl/api/spec/spec.go

@@ -19,7 +19,7 @@ type (
 		Comment Doc
 	}
 
-	// ApiSpec describes a api file
+	// ApiSpec describes an api file
 	ApiSpec struct {
 		Info    Info
 		Syntax  ApiSyntax
@@ -129,7 +129,7 @@ type (
 		Value   Type
 	}
 
-	// InterfaceType describes a interface for api
+	// InterfaceType describes an interface for api
 	InterfaceType struct {
 		RawName string
 	}