Prombench: The go version in prometheus' .promu.yml is not respected

[roidelapluie]

I have noticed that prombench for 2.18.0 did run with go 1.13 instead of go 1.14.

The version in .promu.yml was 1.14. We should respect that, so we can test against the relevant go versions.

[geekodour]

I am a little confused about how it ran with 1.13 It should've ran with 1.15.

test-infra/tools/prometheus-builder/Dockerfile

Line 1 in c162e41

FROM golang:1.15

test-infra/tools/prometheus-builder/build.sh

Lines 26 to 30 in c162e41

	echo ">> Creating prometheus binaries"
	if ! make build PROMU_BINARIES="prometheus"; then
	echo "ERROR:: Building of binaries failed"
	exit 1;
	fi

But this is not a issue if we're comparing the issue against the docker image that is prebuilt because it then directly uses it. Building only occurs for the PR version of prometheus.

test-infra/prombench/manifests/prombench/benchmark/3b_prometheus-test_deployment.yaml

Lines 149 to 152 in c162e41

	containers:
	- name: prometheus
	image: quay.io/prometheus/prometheus:{{ .RELEASE }}
	imagePullPolicy: Always

Am I understanding this wrong?