code: func (c *Context) GetPostForm(key string) (string, bool) {
  	if values, ok := c.GetPostFormArray(key); ok {
  		return values[0], ok
  	}
  	return "", false
  }
docs: // GetPostForm is like PostForm(key). It returns the specified key from a POST urlencoded
  // form or multipart form when it exists `(value, true)` (even when the value is an empty string),
  // otherwise it returns ("", false).
  // For example, during a PATCH request to update the user's email:
  //     email=mail@example.com  -->  ("mail@example.com", true) := GetPostForm("email") // set email to "mail@example.com"
  // 	   email=                  -->  ("", true) := GetPostForm("email") // set email to ""
  //                             -->  ("", false) := GetPostForm("email") // do nothing with email