Add support to envsub go management configurations (#2708)

This change allows users to reference environment variables using Go template format, like {{ .EnvName }}

Moved the previous file test code to file_suite_test.go.

util/file.go

@@ -1,11 +1,15 @@
 package util
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
+	"fmt"
 	"io"
 	"os"
 	"path/filepath"
+	"strings"
+	"text/template"
 
 	log "github.com/sirupsen/logrus"
 )
@@ -160,6 +164,55 @@ func ReadJson(file string, res interface{}) (interface{}, error) {
 	return res, nil
 }
 
+// ReadJsonWithEnvSub reads JSON config file and maps to a provided interface with environment variable substitution
+func ReadJsonWithEnvSub(file string, res interface{}) (interface{}, error) {
+	envVars := getEnvMap()
+
+	f, err := os.Open(file)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	bs, err := io.ReadAll(f)
+	if err != nil {
+		return nil, err
+	}
+
+	t, err := template.New("").Parse(string(bs))
+	if err != nil {
+		return nil, fmt.Errorf("error parsing template: %v", err)
+	}
+
+	var output bytes.Buffer
+	// Execute the template, substituting environment variables
+	err = t.Execute(&output, envVars)
+	if err != nil {
+		return nil, fmt.Errorf("error executing template: %v", err)
+	}
+
+	err = json.Unmarshal(output.Bytes(), &res)
+	if err != nil {
+		return nil, fmt.Errorf("failed parsing Json file after template was executed, err: %v", err)
+	}
+
+	return res, nil
+}
+
+// getEnvMap Convert the output of os.Environ() to a map
+func getEnvMap() map[string]string {
+	envMap := make(map[string]string)
+
+	for _, env := range os.Environ() {
+		parts := strings.SplitN(env, "=", 2)
+		if len(parts) == 2 {
+			envMap[parts[0]] = parts[1]
+		}
+	}
+
+	return envMap
+}
+
 // CopyFileContents copies contents of the given src file to the dst file
 func CopyFileContents(src, dst string) (err error) {
 	in, err := os.Open(src)