added FirstCaseToLowercase naming strategy

extra/naming_strategy.go

@@ -18,7 +18,7 @@ type namingStrategyExtension struct {
 
 func (extension *namingStrategyExtension) UpdateStructDescriptor(structDescriptor *jsoniter.StructDescriptor) {
 	for _, binding := range structDescriptor.Fields {
-		if unicode.IsLower(rune(binding.Field.Name()[0])) || binding.Field.Name()[0] == '_'{
+		if unicode.IsLower(rune(binding.Field.Name()[0])) || binding.Field.Name()[0] == '_' {
 			continue
 		}
 		tag, hastag := binding.Field.Tag().Lookup("json")
@@ -53,3 +53,16 @@ func LowerCaseWithUnderscores(name string) string {
 	}
 	return string(newName)
 }
+
+// FirstCaseToLower one strategy to SetNamingStrategy for. It will change HelloWorld to helloWorld.
+func FirstCaseToLower(name string) string {
+	newName := []rune{}
+	for i, c := range name {
+		if i == 0 {
+			newName = append(newName, unicode.ToLower(c))
+		} else {
+			newName = append(newName, c)
+		}
+	}
+	return string(newName)
+}

extra/naming_strategy_test.go

@@ -64,3 +64,22 @@ func Test_set_naming_strategy_with_private_field(t *testing.T) {
 	should.Nil(err)
 	should.Equal(`{"user_name":"allen"}`, string(output))
 }
+
+func Test_first_case_to_lower(t *testing.T) {
+	should := require.New(t)
+	should.Equal("helloWorld", FirstCaseToLower("HelloWorld"))
+	should.Equal("hello_World", FirstCaseToLower("Hello_World"))
+}
+
+func Test_first_case_to_lower_with_first_case_already_lowercase(t *testing.T) {
+	should := require.New(t)
+	should.Equal("helloWorld", FirstCaseToLower("helloWorld"))
+}
+
+func Test_first_case_to_lower_with_first_case_be_anything(t *testing.T) {
+	should := require.New(t)
+	should.Equal("_HelloWorld", FirstCaseToLower("_HelloWorld"))
+	should.Equal("*HelloWorld", FirstCaseToLower("*HelloWorld"))
+	should.Equal("?HelloWorld", FirstCaseToLower("?HelloWorld"))
+	should.Equal(".HelloWorld", FirstCaseToLower(".HelloWorld"))
+}