1. First impressions of Go
OGAWA Yusaku

2. About me
● OGAWA Yusaku
● HDE, Inc.
● Newbie gopher

3. So good
● Go commands
○ go build
○ go run
○ go fmt
○ go test
○ go get
○ etc.

4. So good: go fmt
$ go fmt main.go
<Before> <After>
package main
import "fmt"
func main(){
sum:=0
for i:=0;i<10;i++{sum+=i}
fmt.Println(sum)
}
package main
import "fmt"
func main() {
sum := 0
for i := 0; i < 10; i++ {
sum += i
}
fmt.Println(sum)
}

5. So good: go test
$ ls
foo.go foo_test.go
$ go test
PASS
ok _/path/to/src/foo 0.027s

6. Good habit

7. Not so good (for me)
● Library
○ The standard library
(In genaral, good enough for writing code, but...)
○ Third-party libraries

8. Not so good: The standard library
● net/mail (Mail parsing library)
http://golang.org/pkg/net/mail/
eml, _ := os.Open("hello.eml")
msg, _ := mail.ReadMessage(eml)
msg.Header.Get("Subject")

9. <Mail>
Received: from example.net ([x.x.x.x])
by example.org (foo); Fri, 30 May 2014 00:00:00 +0900 (JST)
Received: from example.com ([y.y.y.y])
by example.net (bar); Fri, 30 May 2014 00:00:00 +0900 (JST)
Date: Fri, 30 May 2014 00:00:00 +0900
From: from <from@example.com>
Subject: This is a subject header
Hello
<Output>
msg.Header.Get("Subject")
=> This is a subject header
msg.Header.Get("Received")
=> Received: from example.net ([x.x.x.x])
by example.org (foo); Fri, 30 May 2014 00:00:00 +0900 (JST)

10. http://golang.org/src/pkg/net/mail/message.go#L103
103
104 // A Header represents the key-value pairs in a mail message header.
105 type Header map[string][]string
106

11. <UTF-8>
=?UTF-8?B?SGVsbG8sIEdvbGFuZy4=?=
=> Hello, Golang.
<ISO-2022-JP>
=?ISO-2022-JP?B?GyRCJE8kbSE8GyhCLCBHb2xhbmcu?=
=> Error: missing word in phrase
http://golang.org/src/pkg/net/mail/message.go#L445
445 charset, enc := strings.ToLower(fields[1]), strings.ToLower(fields[2])
446 if charset != "iso-8859-1" && charset != "utf-8" {
447 return "", fmt.Errorf("mail: charset not supported: %q", charset)
448 }

12. Not so good: Thirt-party libraries
There are too many standards
● e.g. Iconv bindings for Go
○ github.com/qiniu/iconv
○ github.com/djimenez/iconv-go
○ github.com/xushiwei/go-iconv
○ github.com/hwch/iconv
○ github.com/xuyu/iconv
○ github.com/erkl/iconv
○ github.com/moovweb/goconv
○ github.com/ChaimHong/go-iconv
○ github.com/zhigangc/goconv
○ github.com/vedranvuk/bindiconv
○ github.com/jhiter/goiconv
http://www.xkcd.com/927/

13. Thank you