exit if the CANVAS environment variables are not set

aplus.go

@@ -8,8 +8,8 @@ import (
 	"net/http"
 	"net/url"
 	"regexp"
-	"strings"
 	"strconv"
+	"strings"
 	"time"
 )
 

canvas.go

@@ -15,8 +15,18 @@ import (
 
 func initialize() {
 	instance_url := os.Getenv("CANVAS_INSTANCE")
+	if len(instance_url) == 0 {
+		fmt.Println("The CANVAS_INSTANCE environment variable seems to be empty. Exiting.")
+		os.Exit(1)
+	}
+
 	base_link = instance_url + "/api/v1"
 	token = os.Getenv("CANVAS_API_KEY")
+	if len(token) == 0 {
+		fmt.Println("The CANVAS_API_KEY environment variable seems to be empty. Exiting.")
+		os.Exit(1)
+	}
+
 	jar, _ := cookiejar.New(&cookiejar.Options{
 		PublicSuffixList: publicsuffix.List,
 	})