From your releaser file, amd64 architecture is renamed to x86_64.
It would be easy to use your tool if it follows the release "standard" from Terraform which is compliant with the use of the Docker native args TARGETARCH and TARGETOS, to build multi-architecture container images.
Example
wget -O terraform.zip https://releases.hashicorp.com/terraform/${TERRAFORM_VERSION}/terraform_${TERRAFORM_VERSION}_${TARGETOS}_${TARGETARCH}.zip