solution: allow to setup with ssl

src/main/kotlin/io/emeraldpay/dshackle/GrpcServer.kt

@@ -2,17 +2,21 @@ package io.emeraldpay.dshackle
 
 import io.grpc.Server
 import io.grpc.ServerBuilder
+import org.apache.commons.lang3.StringUtils
 import org.slf4j.LoggerFactory
 import org.springframework.beans.factory.annotation.Autowired
+import org.springframework.core.env.Environment
 import org.springframework.core.io.ResourceLoader
 import org.springframework.stereotype.Service
+import java.io.File
 import javax.annotation.PostConstruct
 import javax.annotation.PreDestroy
 
 @Service
 open class GrpcServer(
         @Autowired val rpcs: List<io.grpc.BindableService>,
-        @Autowired val resourceLoader: ResourceLoader
+        @Autowired val resourceLoader: ResourceLoader,
+        @Autowired val env: Environment
 ) {
 
     private val log = LoggerFactory.getLogger(GrpcServer::class.java)
@@ -27,11 +31,28 @@ open class GrpcServer(
             serverBuilder.addService(it)
         }
 
-//        serverBuilder
-//                .useTransportSecurity(
-//                        resourceLoader.getResource("127.0.0.1.crt").inputStream,
-//                        resourceLoader.getResource("127.0.0.1.p8.key").inputStream
-//                )
+        var secure = false
+        if (env.getProperty("ssl", "false") == "true") {
+            secure = true
+            if (StringUtils.isEmpty(env.getProperty("ssl.cert"))) {
+                log.warn("ssl.cert property is not set (path to server TLS certificate)")
+                secure = false
+            }
+            if (StringUtils.isEmpty(env.getProperty("ssl.key"))) {
+                log.warn("ssl.key property is not set (path to server TLS certificate key)")
+                secure = false
+            }
+        }
+        if (secure) {
+            log.info("Using TLS")
+            serverBuilder
+                    .useTransportSecurity(
+                            File(env.getProperty("ssl.cert")!!),
+                            File(env.getProperty("ssl.key")!!)
+                    )
+        } else {
+            log.warn("Using insecure transport")
+        }
 
         val server = serverBuilder.build()
         this.server = server