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/params/shadowsocks.go

@@ -0,0 +1,40 @@
+package params
+
+import (
+	"strconv"
+
+	libparams "github.com/qdm12/golibs/params"
+)
+
+// GetShadowSocks obtains if ShadowSocks is on from the environment variable
+// SHADOWSOCKS
+func (p *paramsReader) GetShadowSocks() (activated bool, err error) {
+	return p.envParams.GetOnOff("SHADOWSOCKS", libparams.Default("off"))
+}
+
+// GetShadowSocksLog obtains the ShadowSocks log level from the environment variable
+// SHADOWSOCKS_LOG
+func (p *paramsReader) GetShadowSocksLog() (activated bool, err error) {
+	return p.envParams.GetOnOff("SHADOWSOCKS_LOG", libparams.Default("off"))
+}
+
+// GetShadowSocksPort obtains the ShadowSocks listening port from the environment variable
+// SHADOWSOCKS_PORT
+func (p *paramsReader) GetShadowSocksPort() (port uint16, err error) {
+	portStr, err := p.envParams.GetEnv("SHADOWSOCKS_PORT", libparams.Default("8388"))
+	if err != nil {
+		return 0, err
+	}
+	if err := p.verifier.VerifyPort(portStr); err != nil {
+		return 0, err
+	}
+	portUint64, err := strconv.ParseUint(portStr, 10, 16)
+	return uint16(portUint64), err
+}
+
+// GetShadowSocksPassword obtains the ShadowSocks server password from the environment variable
+// SHADOWSOCKS_PASSWORD
+func (p *paramsReader) GetShadowSocksPassword() (password string, err error) {
+	defer p.unsetEnv("SHADOWSOCKS_PASSWORD")
+	return p.envParams.GetEnv("SHADOWSOCKS_PASSWORD")
+}