feat: allow to use env variables in config

api/internal/conf/conf.go

@@ -22,10 +22,12 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"reflect"
 	"runtime"
 	"strings"
 
 	"github.com/gorilla/sessions"
+	"github.com/mitchellh/mapstructure"
 	"github.com/spf13/viper"
 	"github.com/tidwall/gjson"
 	"golang.org/x/oauth2"
@@ -184,6 +186,16 @@ func InitConf() {
 	initSchema()
 }
 
+func unmarshalConfig() (*Config, error) {
+	config := Config{}
+	err := viper.Unmarshal(&config, viper.DecodeHook(substituteEnvironmentVariables()))
+	if err != nil {
+		return nil, err
+	}
+
+	return &config, nil
+}
+
 func setupConfig() {
 	// setup config file path
 	if ConfigFile == "" {
@@ -204,8 +216,7 @@ func setupConfig() {
 	}
 
 	// unmarshal config
-	config := Config{}
-	err := viper.Unmarshal(&config)
+	config, err := unmarshalConfig()
 	if err != nil {
 		panic(fmt.Sprintf("fail to unmarshal configuration: %s, err: %s", ConfigFile, err.Error()))
 	}
@@ -432,3 +443,18 @@ func initSecurity(conf Security) {
 		ContentSecurityPolicy: DefaultCSP,
 	}
 }
+
+// substituteEnvironmentVariables substitutes environment variables in the configuration with real values
+func substituteEnvironmentVariables() mapstructure.DecodeHookFuncKind {
+	return func(
+		f reflect.Kind,
+		t reflect.Kind,
+		data interface{},
+	) (interface{}, error) {
+		if f != reflect.String {
+			return data, nil
+		}
+
+		return os.ExpandEnv(data.(string)), nil
+	}
+}

api/internal/conf/conf_test.go

@@ -1,9 +1,12 @@
 package conf
 
 import (
+	"bytes"
 	"encoding/json"
+	"os"
 	"testing"
 
+	"github.com/spf13/viper"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -61,3 +64,64 @@ func Test_mergeSchema(t *testing.T) {
 		})
 	}
 }
+
+func Test_unmarshalConfig(t *testing.T) {
+	tests := []struct {
+		name   string
+		init   func()
+		config []byte
+		assert func(*Config, *testing.T)
+	}{
+		{
+			name:   "should correctly parse config without environment variables",
+			init:   func() {},
+			config: []byte("conf:\n  listen:\n    port: \"9000\""),
+			assert: func(config *Config, t *testing.T) {
+				assert.Equal(t, 9000, config.Conf.Listen.Port)
+			},
+		},
+		{
+			name: "should correctly substitute int port from environment variables",
+			init: func() {
+				os.Setenv("PORT", "8080")
+			},
+			config: []byte("conf:\n  listen:\n    port: \"$PORT\""),
+			assert: func(config *Config, t *testing.T) {
+				assert.Equal(t, 8080, config.Conf.Listen.Port)
+			},
+		},
+		{
+			name: "should correctly substitute string etcd endpoint from environment variables",
+			init: func() {
+				os.Setenv("ETCD_ENDPOINT", "127.0.0.1:2379")
+			},
+			config: []byte("conf:\n  etcd:\n    endpoints:\n      - $ETCD_ENDPOINT"),
+			assert: func(config *Config, t *testing.T) {
+				assert.Equal(t, "127.0.0.1:2379", config.Conf.Etcd.Endpoints[0])
+			},
+		},
+	}
+
+	for _, tt := range tests {
+
+		t.Run(tt.name, func(t *testing.T) {
+			viper.SetConfigType("yaml")
+			viper.AutomaticEnv()
+
+			tt.init()
+
+			err := viper.ReadConfig(bytes.NewBuffer(tt.config))
+			if err != nil {
+				t.Errorf("unable to read config: %v", err)
+				return
+			}
+			config, err := unmarshalConfig()
+			if err != nil {
+				t.Errorf("unable to unmarshall config: %v", err)
+				return
+			}
+
+			tt.assert(config, t)
+		})
+	}
+}