code: func (c *Context) Header(key, value string) {
  	if value == "" {
  		c.Writer.Header().Del(key)
  		return
  	}
  	c.Writer.Header().Set(key, value)
  }
docs: // Header is a intelligent shortcut for c.Writer.Header().Set(key, value).
  // It writes a header in the response.
  // If value == "", this method removes the header `c.Writer.Header().Del(key)`