Griffin xieyuschen

curl -v http://127.0.0.1:8080/hijack works well, but the curl -v --http2-prior-knowledge http://127.0.0.1:8080/hijack will panic.

func main() {
	e := gin.New()
	e.GET("/hijack", func(context *gin.Context) {
		conn, buf, err := context.Writer.Hijack()
		if err != nil {
 panic(err)

IO.Discard Versus Writing /Dev/Null

Both of them could write down nothing, however, there is still a effieciency difference. Look at the bench:

package base

import (
	"io"
	"os"
	"testing"

Haskell: difference between return/pure and lift

In the following code snippet, return/pure cannot work as it constructs StateT s IO (IO ()), not StateT s IO ().

return/pure will construct the value based on the currect monad in context, which is StateT s IO. lift will upgrade the current monad(IO) to the new monad through the transformer.

printState :: Show s => StateT s IO ()
printState = do
 state &lt;- get

Haskell: why we need a monad transoformer?

When learning the haskell monad transformer(would call it monadt in the left content), a problem in my mind is why monadT? Because from a simple example view, we could make a pale of monad together to do what we want we want to do.

Technially, it's correct, the monadT is just a wrapper. For example, those two cases are equal.

ioOp :: IO String
ioOp = getLine

maybeOp :: Maybe String -&gt; Maybe String

Incrementally Update Struct Golang

增量删除是很重要的，比如说在update的方法里面会出现这样的情况。

type demoStruct struct {
	Replaced string
	Remain   string
}
func main() {
	oldInfo := demoStruct{Replaced: "You can see me no more", Remain: "I still here"}
	fmt.Println(oldInfo.Replaced," ",oldInfo.Remain)

Gin: download file with an simple api

func DownloadLicense(ctx *gin.Context) {
	content:="Download file here happliy"
	fileName := "hello.txt"
	ctx.Header("Content-Disposition", "attachment; filename="+fileName)
	ctx.Header("Content-Type", "application/text/plain")
	ctx.Header("Accept-Length", fmt.Sprintf("%d", len(content)))
	ctx.Writer.Write([]byte(content))
	ctx.JSON(http.StatusOK, gin.H{

Nginx处理跨域请求

在过去处理跨域问题上，只要在nginx中加入如下内容，就可以解决跨域的问题：

add_header Access-Control-Allow-Origin *;
add_header Access-Control-Allow-Headers X-Requested-With;
add_header Access-Control-Allow-Methods GET,POST,OPTIONS;

那么根据上篇文章,使用一个OPTIONS的方法就可以获取到一些跨域的内容，然后浏览器经过预处理之后，就可以完成跨域的操作。这个经过实践应该来说是没有问题的，但写这个贴子希望可以稍微深入一点了解这个请求的内容是如何被nginx加上去的。

	Due to the method of `UnimplementedUserServiceServer` interface isn't exported, we need to run
	the shell here to manipulate the generated file again:

	```shell
	sed -i '' '/type MockUserServiceServer struct {/,/}/ {
	/type MockUserServiceServer struct {/!b
	a\
	\tholepb.UnimplementedUserServiceServer
	}' proto/mockedpb/api_grpc.pb.go
	```

	package main

	import (
	"bytes"
	"fmt"
	"github.com/mitchellh/go-ps"
	"io"
	"os"
	)

	{-# LANGUAGE BlockArguments #-}
	import System.Process
	import Data.Text.IO (hGetLine)
	import GHC.IO.Handle (isEOF, hGetLine)
	import GHC.IO.Handle.Types (Handle)
	import Data.Type.Equality (outer)

	main :: IO ()
	main = do
	(_, out , _, _) <- createProcess (proc "ls" []){ std_out = CreatePipe }