There are two ways. The easy one is to use the -run flag and provide a pattern matching names of the tests you want to run.
Example:
$ go test packageName -run NameOfTest
See the docs for more info.
Note that the -run flag may also run other tests if they contain the string NameOfTest, as the -run flag matches a regexp.
So to ensure that only a test named exactly 'NameOfTest' is run,
one has to use the regexp ^NameOfTest$:
$ go test -run "^NameOfTest$"
The other way is to name the specific file, containing the tests you want to run:
$ go test foo_test.go
But there's a catch. This works well if:
foo.go is in package foo.
foo_test.go is in package foo_test and imports 'foo'.
If foo_test.go and foo.go are the same package (a common case) then you must name all other files required to build foo_test. In this example it would be:
$ go test foo_test.go foo.go
I'd recommend to use the -run pattern. Or, where/when possible, always run all package tests.