Travis build fails

err.txt

0.04s$ $HOME/gopath/bin/goveralls -coverprofile=coverage.out -service=travis-ci -repotoken $COVERALLS_TOKEN
flag needs an argument: -repotoken
Usage: /home/travis/gopath/bin/goveralls [options]
  -covermode string
    	sent as covermode argument to go test (default "count")
  -coverprofile string
    	If supplied, use a go cover profile (comma separated)
  -debug
    	Enable debug output
  -endpoint string
    	Hostname to submit Coveralls data to (default "https://coveralls.io")
  -flags value
    	extra flags to the tests
  -ignore string
    	Comma separated files to ignore
  -package string
    	Go package
  -race
    	Pass '-race' argument to 'go test'
  -repotoken string
    	Repository Token on coveralls
  -service string
    	The CI service or other environment in which the test suite was run.  (default "travis-ci")
  -shallow
    	Shallow coveralls internal server errors
  -v	Pass '-v' argument to 'go test' and output to stdout
The command "$HOME/gopath/bin/goveralls -coverprofile=coverage.out -service=travis-ci -repotoken $COVERALLS_TOKEN" exited with 2.