How to add code to a go template dynamically - templates

Question

I have a go template like follows
apiVersion: apps/v1
kind: Deployment
metadata:
name: {{ include "mychart.fullname" . }}
labels:
app.kubernetes.io/name: {{ include "mychart.name" . }}
helm.sh/chart: {{ include "mychart.chart" . }}
app.kubernetes.io/instance: {{ .Release.Name }}
app.kubernetes.io/managed-by: {{ .Release.Service }}
spec:
replicas: {{ .Values.replicaCount }}
selector:
matchLabels:
app.kubernetes.io/name: {{ include "mychart.name" . }}
app.kubernetes.io/instance: {{ .Release.Name }}
template:
metadata:
labels:
app.kubernetes.io/name: {{ include "mychart.name" . }}
app.kubernetes.io/instance: {{ .Release.Name }}
spec:
containers:
- name: {{ .Chart.Name }}
image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
imagePullPolicy: {{ .Values.image.pullPolicy }}
<-------------------------- Here --------------------------------->
ports:
- name: http
containerPort: 80
protocol: TCP
livenessProbe:
httpGet:
path: /
port: http
readinessProbe:
httpGet:
path: /
port: http
resources:
{{- toYaml .Values.resources | nindent 12 }}
{{- with .Values.nodeSelector }}
nodeSelector:
{{- toYaml . | nindent 8 }}
{{- end }}
{{- with .Values.affinity }}
affinity:
{{- toYaml . | nindent 8 }}
{{- end }}
{{- with .Values.tolerations }}
tolerations:
{{- toYaml . | nindent 8 }}
{{- end }}
I want to add the following piece of code into it, just below imagePullPolicy line. Any ideas ?
env:
- name: NODE_ENV
value: "{{ .Values.node_env }}"
Backgroud:
This above code snippet is helm generated deployment.yaml file, which is used to deploy apps to kubernetes.
Basically what I am trying to achieve is making a script that can set all such stuff in helm chart, so things like adding an environment variable can be done in one go.

Answer 1

Here's a simplified example. The defines and ends are on the same line as the template content to avoid extra blank lines.
main.yaml:
{{define "main"}}apiVersion: apps/v1
spec:
template:
spec:
containers:
- name: foo
{{template "env" .Values}}
ports:
- name: http
containerPort: 80
protocol: TCP
{{end}}
env.yaml:
{{define "env"}} env:
- name: NODE_ENV
value: "{{ .node_env }}"{{end}}
main.go:
package main
import (
"log"
"os"
"text/template"
)
type Deployment struct {
Values map[string]string
}
func main() {
dep := Deployment{Values: map[string]string{
"node_env": "PROD",
}}
tmpl, err := template.ParseFiles("main.yaml", "env.yaml")
if err != nil {
log.Fatal(err)
}
tmpl.ExecuteTemplate(os.Stdout, "main", dep)
if err != nil {
log.Fatal(err)
}
}