Go Test - empty coverage file

I have a test directory in a go project which consist of a single sample test file. I want go see/generate coverage report. Following command is being used to run tests

go test -coverprofile=coverage.out

Output on terminal is

PASS
coverage: 100.0% of statements

coverage.out is getting generated but it consist only single line

mode: set

coverage.out should have information about the files,lines,etc.

Anything that I am doing wrong here?