gin_mock_post.go

func MockJsonPost(c *gin.Context, content interface{}) {
	c.Request.Method = "POST"
	c.Request.Header.Set("Content-Type", "application/json")
	c.Set("user_id", 1)

	jsonbytes, err := json.Marshal(content)
	if err != nil {
		panic(err)
	}

	// the request body must be an io.ReadCloser
	// the bytes buffer though doesn't implement io.Closer,
	// so you wrap it in a no-op closer
	c.Request.Body = io.NopCloser(bytes.NewBuffer(jsonbytes))
}