adjust error handling

cmd/root.go

@@ -22,6 +22,7 @@ import (
 	"go/ast"
 	"go/parser"
 	"go/token"
+	"log"
 	"os"
 	"path/filepath"
 
@@ -106,7 +107,7 @@ func constructDependencyGraph(typesUsed map[filename][]typename, declaredAt map[
 
 			declFile, ok := declaredAt[t]
 			if !ok {
-				return nil, errors.New(string(t) + " not found")
+				return nil, errors.New("did not find declaration for " + string(t))
 			}
 
 			if fname == declFile {
@@ -130,7 +131,7 @@ func parse(cmd *cobra.Command, args []string) {
 	fset := token.NewFileSet()
 	pkgs, err := parser.ParseDir(fset, pkg, nil, 0)
 	if err != nil {
-		panic(err)
+		log.Fatal(err)
 	}
 
 	typesUsed := make(map[filename][]typename)
@@ -174,13 +175,12 @@ func parse(cmd *cobra.Command, args []string) {
 
 	depGraph, err := constructDependencyGraph(typesUsed, declaredAt, ignores)
 	if err != nil {
-		// TODO: handle this error better
-		panic(err)
+		log.Fatal(err)
 	}
 
 	viz, err := dot.Marshal(depGraph, "deps", "", "\t")
 	if err != nil {
-		panic(err)
+		log.Fatal(err)
 	}
 
 	fmt.Println(string(viz))