Official Golang images are now only available for 3.18 and 3.17;
3.18 doesn't look to play well with gotestsum, so sticking to
an older version.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit acb248f)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

go1.20.5 (released 2023-06-06) includes four security fixes to the cmd/go and
runtime packages, as well as bug fixes to the compiler, the go command, the
runtime, and the crypto/rsa, net, and os packages. See the Go 1.20.5 milestone
on our issue tracker for details:

https://github.com/golang/go/issues?q=milestone%3AGo1.20.5+label%3ACherryPickApproved

full diff: golang/go@go1.20.4...go1.20.5

These minor releases include 3 security fixes following the security policy:

- cmd/go: cgo code injection
  The go command may generate unexpected code at build time when using cgo. This
  may result in unexpected behavior when running a go program which uses cgo.

  This may occur when running an untrusted module which contains directories with
  newline characters in their names. Modules which are retrieved using the go command,
  i.e. via "go get", are not affected (modules retrieved using GOPATH-mode, i.e.
  GO111MODULE=off, may be affected).

  Thanks to Juho Nurminen of Mattermost for reporting this issue.

  This is CVE-2023-29402 and Go issue https://go.dev/issue/60167.

- runtime: unexpected behavior of setuid/setgid binaries

  The Go runtime didn't act any differently when a binary had the setuid/setgid
  bit set. On Unix platforms, if a setuid/setgid binary was executed with standard
  I/O file descriptors closed, opening any files could result in unexpected
  content being read/written with elevated prilieges. Similarly if a setuid/setgid
  program was terminated, either via panic or signal, it could leak the contents
  of its registers.

  Thanks to Vincent Dehors from Synacktiv for reporting this issue.

  This is CVE-2023-29403 and Go issue https://go.dev/issue/60272.

- cmd/go: improper sanitization of LDFLAGS

  The go command may execute arbitrary code at build time when using cgo. This may
  occur when running "go get" on a malicious module, or when running any other
  command which builds untrusted code. This is can by triggered by linker flags,
  specified via a "#cgo LDFLAGS" directive.

  Thanks to Juho Nurminen of Mattermost for reporting this issue.

  This is CVE-2023-29404 and CVE-2023-29405 and Go issues https://go.dev/issue/60305 and https://go.dev/issue/60306.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit 3b8d5da)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>