什么是 Golang Comparable Types

Golang 中有很多时候要用到comparable types，例如比较struct的时候，例如map里的 key。弄清楚有哪些类型是comparable的非常重要。

https://golang.org/ref/spec#Comparison_operators

• Boolean values
• Integer values
• Floating point values
• Complex values
• String values
• Pointer values
• Channel values
• Interface values
• Struct values are comparable if all their fields are comparable
• Array values are comparable if values of the array element type are comparable
• A value x of non-interface type X and a value t of interface type T are comparable when values of type X are comparable and X implements T