新增于: v0.4.0
设置单个标头值。
如果待发送标头中已经存在该标头,则替换其值。
使用字符串数组发送多个同名标头。
Added in: v0.4.0
Sets a single header value. If the header already exists in the to-be-sent
headers, its value will be replaced. Use an array of strings to send multiple
headers with the same name.