Go笔记

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// https://stackoverflow.com/questions/33426977/how-to-golang-check-a-variable-is-nil
package main

import (
    "bytes"
    "net/http"
)


func main() {
    client := &http.Client{}
    var content *bytes.Reader
    content = nil
    // it's error
    // req, _ := http.NewRequest("GET", "http://www.github.com", content)
    // it's ok
    req, _ := http.NewRequest("GET", "http://www.github.com", nil)
    resp, _ := client.Do(req)
    defer resp.Body.Close()
}


// A go interface consists of a type and a value. An interface is only nil if both the type and the value are nil. You provided a type but no value: Therefore NewRequest tried to call Read on a nil struct (the value of the interface).

https://github.com/justinas/alice

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func (c Chain) Then(h http.Handler) http.Handler {
	if h == nil {
		h = http.DefaultServeMux
	}

	for i := range c.constructors {
		h = c.constructors[len(c.constructors)-1-i](h)
	}

	return h
}
// Middleware1(Middleware2(Middleware3(App)))