Update 2.1.md
Update 2.1.md

"Hello, world or 你好，世界 or καλημ ́ρα κóσμ or こんにちは世界\n"
or "Hello, world or 你好，世界\n"
or "Hello, world\n"
?
astaxie/build-web-application-with-golang,astaxie/build-web-application-with-golang,admpub/build-web-application-with-golang,WangKaimin/build-web-application-with-golang,songqii/build-web-application-with-golang,admpub/build-web-application-with-golang,faxriddin/build-web-application-with-golang,WangKaimin/build-web-application-with-golang,songqii/build-web-application-with-golang,admpub/build-web-application-with-golang,faxriddin/build-web-application-with-golang,admpub/build-web-application-with-golang,astaxie/build-web-application-with-golang