Pulumi errors when attempting to use Golang 1.18beta2

[cstclair-tunein]

Hello!

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Issue details

Currently Pulumi is broken when attempting to use Golang 1.18beta2.

It throws the error error: parsing go version: Invalid character(s) found in minor number "18beta2" when you attempt to use Pulumi in any capacity.

❯ pulumi new --force
Please choose a template: aws-go
A minimal AWS Go Pulumi program
This command will walk you through creating a new Pulumi project.

Enter a value or leave blank to accept the (default), and press <ENTER>.
Press ^C at any time to quit.

project name: (pulumi-go-18-issue)
project description: (A minimal AWS Go Pulumi program)
Created project 'pulumi-go-18-issue'

Please enter your desired stack name.
To create a stack in an organization, use the format <org-name>/<stack-name> (e.g. `acmecorp/dev`).
stack name: (dev)
Created stack '[redacted]/dev'

aws:region: The AWS region to deploy into: (us-east-1) us-west-2
Saved config

Installing dependencies...

error: parsing go version: Invalid character(s) found in minor number "18beta2"

Steps to reproduce

1. Install golang 1.18beta2
2. Install pulumi
3. Run pulumi new

Expected: It provisions a pulumi project
Actual: It fails to parse the version and errors.

[cstclair-tunein]

I have tracked this issue down to this file: https://github.com/pulumi/pulumi/blob/master/sdk/go/common/util/goversion/version.go

The problem is two-fold, and will unfortunately require a decision as opposed to just a bug fix.

1. the semver library you are relying on, github.com/blang/semver does not actually properly support the semver spec. For example, if I pass that library a semver of the format: 1.0.0-alpha, it will error. However, this is a valid semver!
2. The Golang language version numbers themselves do not follow semver. That is why 1.18beta2 throws an error: It is not valid according to the semver spec.

The work around I have found: simply trim the beta2 from the version string, like so:

// CheckMinimumGoVersion checks to make sure we are running at least minGoVersion
func CheckMinimumGoVersion(gobin string) error {
	cmd := exec.Command(gobin, "version")
	stdout, err := cmd.Output()
	if err != nil {
		return errors.Wrap(err, "determining go version")
	}

	reg := regexp.MustCompile(`beta[0-9]`)
	res := reg.ReplaceAllString(string(stdout), "")

	return checkMinimumGoVersion(res)
}

However, this is clearly hacky and not suitable for a production product.