Simplify environment merging

src/debugAdapter/goDebug.ts

@@ -315,20 +315,23 @@ class Delve {
 			}
 
 			// read env from disk and merge into env variables
-			let fileEnv = {};
+			let envs = [process.env];
+
 			try {
 				if (typeof launchArgs.envFile === 'string') {
-					fileEnv = parseEnvFiles([launchArgs.envFile]);
+					envs.push(...parseEnvFiles([launchArgs.envFile]));
 				}
 
 				if (launchArgs.envFile instanceof Array) {
-					fileEnv = parseEnvFiles(launchArgs.envFile);
+					envs.push(...parseEnvFiles(launchArgs.envFile));
 				}
 			} catch (e) {
 				return reject(e);
 			}
 
-			let env = Object.assign({}, process.env, fileEnv, launchArgsEnv);
+			envs.push(launchArgsEnv);
+
+			let env = Object.assign({}, ...envs);
 
 			let dirname = isProgramDirectory ? program : path.dirname(program);
 			if (!env['GOPATH'] && (mode === 'debug' || mode === 'test')) {

src/goPath.ts

@@ -142,17 +142,17 @@ export function parseEnvFile(path: string): { [key: string]: string } {
 	}
 }
 
-export function parseEnvFiles(paths: string[]): { [key: string]: string } {
-	let mergedEnv: { [key: string]: any } = {};
+export function parseEnvFiles(paths: string[]): { [key: string]: string }[] {
+	let envs: { [key: string]: any }[] = [];
 
 	for (let i = 0; i < paths.length; i++) {
 		const path = paths[i];
 		let env = parseEnvFile(path);
 
-		mergedEnv = Object.assign(mergedEnv, env);
+		envs.push(env)
 	}
 
-	return mergedEnv;
+	return envs;
 }
 
 // Walks up given folder path to return the closest ancestor that has `src` as a child