yarn command not found in gitlab ci

Add the following to your ci script after yarn got installed:

export PATH=$HOME/.yarn/bin:$PATH

Solved it by using the latest official node docker image. Since image: 6.10.0, yarn is installed by default in the image.

But if you need node-gyp to build any package, it needs to be installed by adding a line to the script:

yarn global add node-gyp