I want to upgrade the kubectl client version to 1.11.3.
I executed brew install kubernetes-cli
but the version doesnt seem to be updating.
Similar to what boraas said. The version you are seeing is from another kubectl.exe installation. I had docker for windows installed which already has kubectl.exe (located in Docker\resources\bin) and was of older version. This gets used unless you provide explicitly the path to the new location of your kubectl.exe [you need to set it in PATH].
Via Chocolatey:
choco upgrade kubernetes-cli