go tool runs specific tool
go tool [-n] command [args...]
列出所有tool
eg .go tool
addr2line
api
asm
buildid
cgo
compile
cover
dist
doc
fix
link
nm
objdump
pack
pprof
test2json
trace
vet
tool用法說明
go tool <command> --help
eg. go tool api --help
tool詳細介紹
go doc cmd/<command>
eg. go doc cmd/api
