diff --git a/.env-sample b/.env-sample
new file mode 100644
index 0000000..9a790b6
--- /dev/null
+++ b/.env-sample
@@ -0,0 +1 @@
+VAR=foo
diff --git a/.gitignore b/.gitignore
index 66fd13c..1a8ec9c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,7 @@
+# Created by https://www.gitignore.io/api/go,vim,xcode,linux,macos,windows,intellij+all,visualstudiocode
+# Edit at https://www.gitignore.io/?templates=go,vim,xcode,linux,macos,windows,intellij+all,visualstudiocode
+
+### Go ###
 # Binaries for programs and plugins
 *.exe
 *.exe~
@@ -13,3 +17,239 @@
 
 # Dependency directories (remove the comment below to include it)
 # vendor/
+
+### Go Patch ###
+/vendor/
+/Godeps/
+
+### Intellij+all ###
+# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio and WebStorm
+# Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839
+
+# User-specific stuff
+.idea/**/workspace.xml
+.idea/**/tasks.xml
+.idea/**/usage.statistics.xml
+.idea/**/dictionaries
+.idea/**/shelf
+
+# Generated files
+.idea/**/contentModel.xml
+
+# Sensitive or high-churn files
+.idea/**/dataSources/
+.idea/**/dataSources.ids
+.idea/**/dataSources.local.xml
+.idea/**/sqlDataSources.xml
+.idea/**/dynamic.xml
+.idea/**/uiDesigner.xml
+.idea/**/dbnavigator.xml
+
+# Gradle
+.idea/**/gradle.xml
+.idea/**/libraries
+
+# Gradle and Maven with auto-import
+# When using Gradle or Maven with auto-import, you should exclude module files,
+# since they will be recreated, and may cause churn.  Uncomment if using
+# auto-import.
+# .idea/modules.xml
+# .idea/*.iml
+# .idea/modules
+# *.iml
+# *.ipr
+
+# CMake
+cmake-build-*/
+
+# Mongo Explorer plugin
+.idea/**/mongoSettings.xml
+
+# File-based project format
+*.iws
+
+# IntelliJ
+out/
+
+# mpeltonen/sbt-idea plugin
+.idea_modules/
+
+# JIRA plugin
+atlassian-ide-plugin.xml
+
+# Cursive Clojure plugin
+.idea/replstate.xml
+
+# Crashlytics plugin (for Android Studio and IntelliJ)
+com_crashlytics_export_strings.xml
+crashlytics.properties
+crashlytics-build.properties
+fabric.properties
+
+# Editor-based Rest Client
+.idea/httpRequests
+
+# Android studio 3.1+ serialized cache file
+.idea/caches/build_file_checksums.ser
+
+### Intellij+all Patch ###
+# Ignores the whole .idea folder and all .iml files
+# See https://github.com/joeblau/gitignore.io/issues/186 and https://github.com/joeblau/gitignore.io/issues/360
+
+.idea/
+
+# Reason: https://github.com/joeblau/gitignore.io/issues/186#issuecomment-249601023
+
+*.iml
+modules.xml
+.idea/misc.xml
+*.ipr
+
+# Sonarlint plugin
+.idea/sonarlint
+
+### Linux ###
+*~
+
+# temporary files which can be created if a process still has a handle open of a deleted file
+.fuse_hidden*
+
+# KDE directory preferences
+.directory
+
+# Linux trash folder which might appear on any partition or disk
+.Trash-*
+
+# .nfs files are created when an open file is removed but is still being accessed
+.nfs*
+
+### macOS ###
+# General
+.DS_Store
+.AppleDouble
+.LSOverride
+
+# Icon must end with two \r
+Icon
+
+# Thumbnails
+._*
+
+# Files that might appear in the root of a volume
+.DocumentRevisions-V100
+.fseventsd
+.Spotlight-V100
+.TemporaryItems
+.Trashes
+.VolumeIcon.icns
+.com.apple.timemachine.donotpresent
+
+# Directories potentially created on remote AFP share
+.AppleDB
+.AppleDesktop
+Network Trash Folder
+Temporary Items
+.apdisk
+
+### Vim ###
+# Swap
+[._]*.s[a-v][a-z]
+[._]*.sw[a-p]
+[._]s[a-rt-v][a-z]
+[._]ss[a-gi-z]
+[._]sw[a-p]
+
+# Session
+Session.vim
+Sessionx.vim
+
+# Temporary
+.netrwhist
+
+# Auto-generated tag files
+tags
+
+# Persistent undo
+[._]*.un~
+
+# Coc configuration directory
+.vim
+
+### VisualStudioCode ###
+.vscode/*
+!.vscode/settings.json
+!.vscode/tasks.json
+!.vscode/launch.json
+!.vscode/extensions.json
+
+### VisualStudioCode Patch ###
+# Ignore all local history of files
+.history
+
+### Windows ###
+# Windows thumbnail cache files
+Thumbs.db
+Thumbs.db:encryptable
+ehthumbs.db
+ehthumbs_vista.db
+
+# Dump file
+*.stackdump
+
+# Folder config file
+[Dd]esktop.ini
+
+# Recycle Bin used on file shares
+$RECYCLE.BIN/
+
+# Windows Installer files
+*.cab
+*.msi
+*.msix
+*.msm
+*.msp
+
+# Windows shortcuts
+*.lnk
+
+### Xcode ###
+# Xcode
+#
+# gitignore contributors: remember to update Global/Xcode.gitignore, Objective-C.gitignore & Swift.gitignore
+
+## User settings
+xcuserdata/
+
+## compatibility with Xcode 8 and earlier (ignoring not required starting Xcode 9)
+*.xcscmblueprint
+*.xccheckout
+
+## compatibility with Xcode 3 and earlier (ignoring not required starting Xcode 4)
+build/
+DerivedData/
+*.moved-aside
+*.pbxuser
+!default.pbxuser
+*.mode1v3
+!default.mode1v3
+*.mode2v3
+!default.mode2v3
+*.perspectivev3
+!default.perspectivev3
+
+## Xcode Patch
+*.xcodeproj/*
+!*.xcodeproj/project.pbxproj
+!*.xcodeproj/xcshareddata/
+!*.xcworkspace/contents.xcworkspacedata
+/*.gcno
+
+### Xcode Patch ###
+**/xcshareddata/WorkspaceSettings.xcsettings
+
+*manager
+
+### .env
+.env
+
+# End of https://www.gitignore.io/api/go,vim,xcode,linux,macos,windows,intellij+all,visualstudiocode
\ No newline at end of file
diff --git a/Makefile b/Makefile
index 8e237a8..fbc2c8d 100644
--- a/Makefile
+++ b/Makefile
@@ -6,7 +6,7 @@ define docker_run
 	@docker run -it --rm \
 	-v "$$(pwd):/app" \
 	-p $(API_PORT):$(API_PORT) \
-	-e VAR=foo \
+	--env-file .env \
 	--name $(APP_NAME) \
 	-w "/app" \
 	golang:$(GO_VERSION) $1
diff --git a/main_test.go b/main_test.go
index 55aaa97..07a11fb 100644
--- a/main_test.go
+++ b/main_test.go
@@ -5,9 +5,11 @@ import (
 )
 
 func TestCalc(t *testing.T) {
-	got := calc(2, 2)
+	t.Run("Failure responses", func(t *testing.T) {
+		got := calc(2, 2)
 
-	if got != 4 {
-		t.Errorf("calc(2, 2) = %d, want 4", got)
-	}
+		if got == 4 {
+			t.Errorf("calc(2, 2) = %d, want 6", got)
+		}
+	})
 }