stringutil 不是个 package 么，哪有 stringutil.gohttp://golang.org/doc/code.html#PackageNames
>> Package names
>> By convention, packages are given lower case, single-word names; there should be no need for underscores or mixedCaps.
>> Finally, the convention in Go is to use MixedCaps or mixedCaps rather than underscores to write multiword names.
>> To write a new test suite, create a file whose name ends _test.go that contains the TestXxx functions as described here.