feat: WithEnv customize request option

Add WithEnv which set additional environment variables on a request
so that callers can customise a request.

This can be used to easily add environment variables to a container
created using one of the standard module e.g. postgres.

docker.go

@@ -561,7 +561,7 @@ func (c *DockerContainer) CopyFileFromContainer(ctx context.Context, filePath st
 
 // CopyDirToContainer copies the contents of a directory to a parent path in the container. This parent path must exist in the container first
 // as we cannot create it
-func (c *DockerContainer) CopyDirToContainer(ctx context.Context, hostDirPath string, containerParentPath string, fileMode int64) error {
+func (c *DockerContainer) CopyDirToContainer(ctx context.Context, hostDirPath, containerParentPath string, fileMode int64) error {
 	dir, err := isDir(hostDirPath)
 	if err != nil {
 		return err
@@ -589,7 +589,7 @@ func (c *DockerContainer) CopyDirToContainer(ctx context.Context, hostDirPath st
 	return nil
 }
 
-func (c *DockerContainer) CopyFileToContainer(ctx context.Context, hostFilePath string, containerFilePath string, fileMode int64) error {
+func (c *DockerContainer) CopyFileToContainer(ctx context.Context, hostFilePath, containerFilePath string, fileMode int64) error {
 	dir, err := isDir(hostFilePath)
 	if err != nil {
 		return err
@@ -1446,7 +1446,6 @@ func (p *DockerProvider) getDefaultNetwork(ctx context.Context, cli client.APICl
 			Attachable: true,
 			Labels:     core.DefaultLabels(core.SessionID()),
 		})
-
 		if err != nil {
 			return "", err
 		}

options.go

@@ -53,6 +53,30 @@ func WithEndpointSettingsModifier(modifier func(settings map[string]*network.End
 	}
 }
 
+// WithEnv sets the environment variables for a container.
+// If the environment variable already exists, it will be overridden.
+// panics if the number of arguments is odd.
+func WithEnv(envs ...string) CustomizeRequestOption {
+	if len(envs)%2 != 0 {
+		panic("WithEnv requires an even number of arguments")
+	}
+
+	return func(req *GenericContainerRequest) {
+		if req.Env == nil {
+			req.Env = map[string]string{}
+		}
+
+		var key string
+		for i, v := range envs {
+			if i%2 == 0 {
+				key = v
+			} else {
+				req.Env[key] = v
+			}
+		}
+	}
+}
+
 // WithHostConfigModifier allows to override the default host config
 func WithHostConfigModifier(modifier func(hostConfig *container.HostConfig)) CustomizeRequestOption {
 	return func(req *GenericContainerRequest) {

options_test.go

@@ -162,3 +162,67 @@ func TestWithAfterReadyCommand(t *testing.T) {
 	require.NoError(t, err)
 	assert.Equal(t, "/tmp/.testcontainers\n", string(content))
 }
+
+func TestWithEnv(t *testing.T) {
+	tests := map[string]struct {
+		req    *testcontainers.GenericContainerRequest
+		env    []string
+		expect map[string]string
+	}{
+		"add": {
+			req: &testcontainers.GenericContainerRequest{
+				ContainerRequest: testcontainers.ContainerRequest{
+					Env: map[string]string{
+						"KEY1": "VAL1",
+					},
+				},
+			},
+			env: []string{
+				"KEY2", "VAL2",
+			},
+			expect: map[string]string{
+				"KEY1": "VAL1",
+				"KEY2": "VAL2",
+			},
+		},
+		"add-nil": {
+			req: &testcontainers.GenericContainerRequest{},
+			env: []string{
+				"KEY2", "VAL2",
+			},
+			expect: map[string]string{
+				"KEY2": "VAL2",
+			},
+		},
+		"override": {
+			req: &testcontainers.GenericContainerRequest{
+				ContainerRequest: testcontainers.ContainerRequest{
+					Env: map[string]string{
+						"KEY1": "VAL1",
+						"KEY2": "VAL2",
+					},
+				},
+			},
+			env: []string{
+				"KEY2", "VAL3",
+			},
+			expect: map[string]string{
+				"KEY1": "VAL1",
+				"KEY2": "VAL3",
+			},
+		},
+	}
+	for name, tc := range tests {
+		t.Run(name, func(t *testing.T) {
+			opt := testcontainers.WithEnv(tc.env...)
+			opt.Customize(tc.req)
+			require.Equal(t, tc.expect, tc.req.Env)
+		})
+	}
+
+	t.Run("odd-args", func(t *testing.T) {
+		require.Panics(t, func() {
+			testcontainers.WithEnv("KEY1")
+		})
+	})
+}

reaper.go

@@ -121,7 +121,6 @@ func lookUpReaperContainer(ctx context.Context, sessionID string) (*DockerContai
 
 		return nil
 	}, backoff.WithContext(exp, ctx))
-
 	if err != nil {
 		return nil, err
 	}