Rewrite of the entrypoint in Golang (#71)

- General improvements
    - Parallel download of only needed files at start
    - Prettier console output with all streams merged (openvpn, unbound, shadowsocks etc.)
    - Simplified Docker final image
    - Faster bootup
- DNS over TLS
    - Finer grain blocking at DNS level: malicious, ads and surveillance
    - Choose your DNS over TLS providers
    - Ability to use multiple DNS over TLS providers for DNS split horizon
    - Environment variables for DNS logging
    - DNS block lists needed are downloaded and built automatically at start, in parallel
- PIA
    - A random region is selected if the REGION parameter is left empty (thanks @rorph for your PR)
    - Routing and iptables adjusted so it can work as a Kubernetes pod sidecar (thanks @rorph for your PR)

internal/pia/modify_test.go

@@ -0,0 +1,31 @@
+package pia
+
+import (
+	"io/ioutil"
+	"net"
+	"strings"
+	"testing"
+
+	loggingMocks "github.com/qdm12/golibs/logging/mocks"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func Test_ModifyLines(t *testing.T) {
+	t.Parallel()
+	original, err := ioutil.ReadFile("testdata/ovpn.golden")
+	require.NoError(t, err)
+	originalLines := strings.Split(string(original), "\n")
+	expected, err := ioutil.ReadFile("testdata/ovpn.modified.golden")
+	require.NoError(t, err)
+	expectedLines := strings.Split(string(expected), "\n")
+
+	var port uint16 = 3000
+	IPs := []net.IP{net.IP{100, 10, 10, 10}, net.IP{100, 20, 20, 20}}
+	logger := &loggingMocks.Logger{}
+	logger.On("Info", "%s: adapting openvpn configuration for server IP addresses and port %d", logPrefix, port).Once()
+	c := &configurator{logger: logger}
+	modifiedLines := c.ModifyLines(originalLines, IPs, port)
+	assert.Equal(t, expectedLines, modifiedLines)
+	logger.AssertExpectations(t)
+}