fixes suggestions by golanglint-ci

main.go

 package main
 
 import (
+	"fmt"
 	"log"
 	"os"
 	"strings"
@@ -32,23 +33,25 @@ func main() {
 				Destination: &outfile,
 			},
 		},
-		Action: func(cCtx *cli.Context) error {
+		Action: func(_ *cli.Context) error {
 			b, err := os.ReadFile(tmpl)
 			if err != nil {
-				return err
+				return fmt.Errorf("failed to read template file: %w", err)
 			}
-			t := template.Must(template.New("tplate").Parse(string(b)))
+
+			tmpl := template.Must(template.New("tplate").Parse(string(b)))
 
 			out, err := os.Create(outfile)
 			if err != nil {
-				return err
+				return fmt.Errorf("failed to create output file: %w", err)
 			}
 			defer out.Close()
 
 			m := makeEnvMap()
-			if err := t.Execute(out, m); err != nil {
-				return err
+			if err := tmpl.Execute(out, m); err != nil {
+				return fmt.Errorf("failed to execute template: %w", err)
 			}
+
 			return nil
 		},
 	}
@@ -63,11 +66,15 @@ type (
 )
 
 func makeEnvMap() EnvMap {
-	m := make(EnvMap)
+	const splitParts = 2
+
+	envMap := make(EnvMap)
 	env := os.Environ()
+
 	for _, e := range env {
-		bits := strings.SplitN(e, "=", 2)
-		m[bits[0]] = bits[1]
+		bits := strings.SplitN(e, "=", splitParts)
+		envMap[bits[0]] = bits[1]
 	}
-	return m
+
+	return envMap
 }