stringutil 不是个 package 么,哪有 stringutil.go
http://golang.org/doc/code.html#PackageNames →
http://golang.org/doc/effective_go.html#names>> Package names
>> By convention, packages are given lower case, single-word names; there should be no need for underscores or mixedCaps.
>> MixedCaps
>> Finally, the convention in Go is to use MixedCaps or mixedCaps rather than underscores to write multiword names.
reverse_test.go 是因为这是测试所以才下划线了吧
http://golang.org/pkg/testing/>> To write a new test suite, create a file whose name ends _test.go that contains the TestXxx functions as described here.