While creating a duplicate deployment system for testing purposes we may require to install a very old version of helm
I have done this by using the below steps.
# curl -fsSL -o get_helm.sh https://raw.githubusercontent.com/helm/helm/master/scripts/get-helm-3
# chmod +x get_helm.sh
# ./get_helm.sh -v v3.1.2
# helm version
version.BuildInfo{Version:"v3.1.2", GitCommit:"d878d4d45863e42fd5cff6743294a11d28a9abce", GitTreeState:"clean", GoVersion:"go1.13.8"}