go struct 与 json
https://golang.org/pkg/encoding/json/#pkg-index
成员标签-tag
https://sosedoff.com/2016/07/16/golang-struct-tags.html
Only data structures that can be represented as valid JSON will be encoded:
JSON objects only support strings as keys; to encode a Go map type it must be of the form map[string]T (where T is any Go type supported by the json package).
// JSON的key只能是string类型，所有在支持Map的情况下，需要其对应的Map的key是string类型。
Channel, complex, and function types cannot be encoded.
// 这些类型是无法被encoded的
Cyclic data structures are not supported; they will cause Marshal to go into an infinite loop.
// 循环数据类型无法被encoded
Pointers will be encoded as the values they point to (or 'null' if the pointer is nil).
// 指针类型可以被encoded
The json package only accesses the exported fields of struct types (those that begin with an uppercase letter). Therefore only the the exported fields of a struct will be present in the JSON output.
// 只能访问那些exported的struct types类型的field（大写字母开头的）
使用
encode
使用marshal方法进行编码。
func Marshal(v interface{}) ([]byte, error)
举例使用一个go定义的一个structure Message
type Message struct {
Name string
Body string
Time int64
}
使用一个Message的实例被编码完以后的结果类似于下面
b == []byte(`{"Name":"Alice","Body":"Hello","Time":1294706395881547000}`)
编码中需要注意的内容
Only data structures that can be represented as valid JSON will be encoded:
JSON objects only support strings as keys; to encode a Go map type it must be of the form map[string]T (where T is any Go type supported by the json package).
// JSON的key只能是string类型，所有在支持Map的情况下，需要其对应的Map的key是string类型。
Channel, complex, and function types cannot be encoded.
// 这些类型是无法被encoded的
Cyclic data structures are not supported; they will cause Marshal to go into an infinite loop.
// 循环数据类型无法被encoded
Pointers will be encoded as the values they point to (or 'null' if the pointer is nil).
// 指针类型可以被encoded
The json package only accesses the exported fields of struct types (those that begin with an uppercase letter). Therefore only the the exported fields of a struct will be present in the JSON output.
// 只能访问那些exported的struct types类型的field（大写字母开头的）
