Add support for environment variables in configuration file

Dockerfile

@@ -13,4 +13,4 @@ COPY --from=builder /app/static static/
 COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
 ENV PORT=8080
 EXPOSE ${PORT}
-ENTRYPOINT ["/gatus"]
+ENTRYPOINT ["/gatus"]

README.md

@@ -17,13 +17,15 @@ services:
     url: https://twinnation.org/actuator/health
     interval: 15s     # Duration to wait between every status check (opt. default: 10s)
     conditions:
-      - "$STATUS == 200"
+      - "[STATUS] == 200"
   - name: github
     url: https://api.github.com/healthz
     conditions:
-      - "$STATUS == 200"
+      - "[STATUS] == 200"
 ```
 
+Note that you can also add environment variables in the your configuration file (i.e. `$DOMAIN`, `${DOMAIN}`)
+
 
 ## Docker
 

config.yaml

@@ -4,8 +4,8 @@ services:
     url: https://twinnation.org/actuator/health
     interval: 15s
     conditions:
-      - "$STATUS == 200"
+      - "[STATUS] == 200"
   - name: github
     url: https://api.github.com/healthz
     conditions:
-      - "$STATUS == 200"
+      - "[STATUS] == 200"

config/config.go

@@ -64,6 +64,9 @@ func readConfigurationFile(fileName string) (config *Config, err error) {
 }
 
 func parseAndValidateConfigBytes(yamlBytes []byte) (config *Config, err error) {
+	// Expand environment variables
+	yamlBytes = []byte(os.ExpandEnv(string(yamlBytes)))
+	// Parse configuration file
 	err = yaml.Unmarshal(yamlBytes, &config)
 	// Check if the configuration file at least has services.
 	if config == nil || len(config.Services) == 0 {

config/config_test.go

@@ -13,12 +13,12 @@ services:
     url: https://twinnation.org/actuator/health
     interval: 15s
     conditions:
-      - "$STATUS == 200"
+      - "[STATUS] == 200"
   - name: github
     url: https://api.github.com/healthz
     conditions:
-      - "$STATUS != 400"
-      - "$STATUS != 500"
+      - "[STATUS] != 400"
+      - "[STATUS] != 500"
 `))
 	if err != nil {
 		t.Error("No error should've been returned")
@@ -53,7 +53,7 @@ services:
   - name: twinnation
     url: https://twinnation.org/actuator/health
     conditions:
-      - "$STATUS == 200"
+      - "[STATUS] == 200"
 `))
 	if err != nil {
 		t.Error("No error should've been returned")
@@ -76,7 +76,7 @@ services:
   - name: twinnation
     url: https://twinnation.org/actuator/health
     conditions:
-      - "$STATUS == 200"
+      - "[STATUS] == 200"
 `))
 	if err != nil {
 		t.Error("No error should've been returned")

core/types.go

@@ -140,9 +140,9 @@ func sanitizeAndResolve(list []string, result *Result) []string {
 	for _, element := range list {
 		element = strings.TrimSpace(element)
 		switch strings.ToUpper(element) {
-		case "$STATUS":
+		case "[STATUS]":
 			element = strconv.Itoa(result.HttpStatus)
-		case "$IP":
+		case "[IP]":
 			element = result.Ip
 		default:
 		}

core/types_test.go

@@ -5,7 +5,7 @@ import (
 )
 
 func TestEvaluateWithIp(t *testing.T) {
-	condition := Condition("$IP == 127.0.0.1")
+	condition := Condition("[IP] == 127.0.0.1")
 	result := &Result{Ip: "127.0.0.1"}
 	condition.Evaluate(result)
 	if !result.ConditionResults[0].Success {
@@ -14,7 +14,7 @@ func TestEvaluateWithIp(t *testing.T) {
 }
 
 func TestEvaluateWithStatus(t *testing.T) {
-	condition := Condition("$STATUS == 201")
+	condition := Condition("[STATUS] == 201")
 	result := &Result{HttpStatus: 201}
 	condition.Evaluate(result)
 	if !result.ConditionResults[0].Success {
@@ -23,7 +23,7 @@ func TestEvaluateWithStatus(t *testing.T) {
 }
 
 func TestEvaluateWithFailure(t *testing.T) {
-	condition := Condition("$STATUS == 200")
+	condition := Condition("[STATUS] == 200")
 	result := &Result{HttpStatus: 500}
 	condition.Evaluate(result)
 	if result.ConditionResults[0].Success {
@@ -32,7 +32,7 @@ func TestEvaluateWithFailure(t *testing.T) {
 }
 
 func TestIntegrationEvaluateConditions(t *testing.T) {
-	condition := Condition("$STATUS == 200")
+	condition := Condition("[STATUS] == 200")
 	service := Service{
 		Name:       "GitHub",
 		Url:        "https://api.github.com/healthz",
@@ -48,7 +48,7 @@ func TestIntegrationEvaluateConditions(t *testing.T) {
 }
 
 func TestIntegrationEvaluateConditionsWithFailure(t *testing.T) {
-	condition := Condition("$STATUS == 500")
+	condition := Condition("[STATUS] == 500")
 	service := Service{
 		Name:       "GitHub",
 		Url:        "https://api.github.com/healthz",

example/docker-compose-grafana-prometheus/config.yaml

@@ -4,12 +4,12 @@ services:
     url: https://twinnation.org/actuator/health
     interval: 10s
     conditions:
-      - "$STATUS == 200"
+      - "[STATUS] == 200"
   - name: GitHub
     url: https://api.github.com/healthz
     conditions:
-      - "$STATUS == 200"
+      - "[STATUS] == 200"
   - name: Example
     url: https://example.com/
     conditions:
-      - "$STATUS == 200"
+      - "[STATUS] == 200"

example/minimal/config.yaml

@@ -3,4 +3,4 @@ services:
     url: http://example.org
     interval: 30s
     conditions:
-      - "$STATUS == 200"
+      - "[STATUS] == 200"