Passing Key-value Program Arguments to Go Programs in Code

May 25, 2016

I’m currently working on Topo, a tool that aids provisioning multiple Terraform configurations of the same project. An example use-case where Topo might be a good solution is: say you want to provision multiple Jenkins servers for different teams, and you want to maintain the state of the resources so you can run Terraform to reapply as the configuration or capacity changes, or destroy.

I’m writing Topo in Go, and I’m using the go-sh package to programmatically run shell processes. All was going well till I had to write the Terraform remote config command for configuring remote state storage in S3. The command looks like this:

terraform remote config \
    -backend=s3 \
    -backend-config="bucket=terraform-state-prod" \
    -backend-config="key=network/terraform.tfstate" \

In my code, I wrote the go-sh command like this:

sh.Command("terraform", "remote", "config",
	"-backend=s3", "-backend-config='bucket=jenkins-bucket'",

That doesn’t work though, and results in this error:

missing 'bucket' configuration

If the error message above mentions requiring or modifying configuration
options, these are set using the `-backend-config` flag. Example:
-backend-config="name=foo" to set the `name` configuration

The Terraform command works perfectly when run the command line. I spent a couple of hours trying stuff out. Terraform is a Go program, and it turns out that Go programs accept flags as key-value pairs(except for booleans) separated by equals sign (“=”). Breaking up the arguments like below from “key=‘value’” to “key”, “value” solves the problem:

sh.Command("terraform", "remote", "config", "-backend=s3",
    "-backend-config", "bucket=jenkins-bucket",
    "-backend-config", "key=jenkins/terraform.tfstate",
comments powered by Disqus