Google's DoH resolver can fail on some devices/networks

[gnarea]

This has happened to Sergio on Android 8.1, but I've been unable to reproduce it on Android 5/8/10 using 2 different lines.

2021-03-31 13:16:01.006 22915-22941/tech.relaycorp.gateway W/heckPublicGatewayAccess: Failed to resolve PoWeb address (Failed to resolve DNS for PoWeb address)
2021-03-31 13:16:01.658 22915-22941/tech.relaycorp.gateway W/RegisterGateway: Could not register gateway due to failure to resolve PoWeb address
    tech.relaycorp.gateway.data.doh.PublicAddressResolutionException: Failed to resolve DNS for PoWeb address
        at tech.relaycorp.gateway.data.doh.ResolveServiceAddress.resolvePoWeb(ResolveServiceAddress.kt:18)
        at tech.relaycorp.gateway.data.doh.ResolveServiceAddress$resolvePoWeb$1.invokeSuspend(Unknown Source:16)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
        at io.ktor.util.pipeline.SuspendFunctionGun.resumeRootWith(SuspendFunctionGun.kt:191)
        at io.ktor.util.pipeline.SuspendFunctionGun.access$resumeRootWith(SuspendFunctionGun.kt:15)
        at io.ktor.util.pipeline.SuspendFunctionGun$continuation$1.resumeWith(SuspendFunctionGun.kt:86)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:46)
        at io.ktor.util.pipeline.SuspendFunctionGun.resumeRootWith(SuspendFunctionGun.kt:191)
        at io.ktor.util.pipeline.SuspendFunctionGun.access$resumeRootWith(SuspendFunctionGun.kt:15)
        at io.ktor.util.pipeline.SuspendFunctionGun$continuation$1.resumeWith(SuspendFunctionGun.kt:86)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:46)
        at io.ktor.util.pipeline.SuspendFunctionGun.resumeRootWith(SuspendFunctionGun.kt:191)
        at io.ktor.util.pipeline.SuspendFunctionGun.access$resumeRootWith(SuspendFunctionGun.kt:15)
        at io.ktor.util.pipeline.SuspendFunctionGun$continuation$1.resumeWith(SuspendFunctionGun.kt:86)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:46)
        at io.ktor.util.pipeline.SuspendFunctionGun.resumeRootWith(SuspendFunctionGun.kt:191)
        at io.ktor.util.pipeline.SuspendFunctionGun.access$resumeRootWith(SuspendFunctionGun.kt:15)
        at io.ktor.util.pipeline.SuspendFunctionGun$continuation$1.resumeWith(SuspendFunctionGun.kt:86)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:46)
        at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:104)
        at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:571)
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:750)
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:678)
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:665)
     Caused by: tech.relaycorp.doh.LookupFailureException: Failed to connect to https://dns.google/dns-query
        at tech.relaycorp.doh.DoHClient.lookUp(DoHClient.kt:58)
        at tech.relaycorp.doh.DoHClient$lookUp$1.invokeSuspend(Unknown Source:12)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33) 
        at io.ktor.util.pipeline.SuspendFunctionGun.resumeRootWith(SuspendFunctionGun.kt:191) 
        at io.ktor.util.pipeline.SuspendFunctionGun.access$resumeRootWith(SuspendFunctionGun.kt:15) 
        at io.ktor.util.pipeline.SuspendFunctionGun$continuation$1.resumeWith(SuspendFunctionGun.kt:86) 
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:46) 
        at io.ktor.util.pipeline.SuspendFunctionGun.resumeRootWith(SuspendFunctionGun.kt:191) 
        at io.ktor.util.pipeline.SuspendFunctionGun.access$resumeRootWith(SuspendFunctionGun.kt:15) 
        at io.ktor.util.pipeline.SuspendFunctionGun$continuation$1.resumeWith(SuspendFunctionGun.kt:86) 
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:46) 
        at io.ktor.util.pipeline.SuspendFunctionGun.resumeRootWith(SuspendFunctionGun.kt:191) 
        at io.ktor.util.pipeline.SuspendFunctionGun.access$resumeRootWith(SuspendFunctionGun.kt:15) 
        at io.ktor.util.pipeline.SuspendFunctionGun$continuation$1.resumeWith(SuspendFunctionGun.kt:86) 
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:46) 
        at io.ktor.util.pipeline.SuspendFunctionGun.resumeRootWith(SuspendFunctionGun.kt:191) 
        at io.ktor.util.pipeline.SuspendFunctionGun.access$resumeRootWith(SuspendFunctionGun.kt:15) 
        at io.ktor.util.pipeline.SuspendFunctionGun$continuation$1.resumeWith(SuspendFunctionGun.kt:86) 
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:46) 
        at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:104) 
        at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:571) 
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:750) 
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:678) 
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:665) 
     Caused by: io.ktor.network.sockets.ConnectTimeoutException: Connect timeout has been expired [url=https://dns.google/dns-query, connect_timeout=unknown ms]
        at io.ktor.client.features.HttpTimeoutKt.ConnectTimeoutException(HttpTimeout.kt:164)
        at io.ktor.client.engine.okhttp.OkUtilsKt$execute$$inlined$suspendCancellableCoroutine$lambda$1.onFailure(OkUtils.kt:29)
        at okhttp3.internal.connection.RealCall$AsyncCall.run(RealCall.kt:525)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
        at java.lang.Thread.run(Thread.java:764)
     Caused by: java.net.SocketTimeoutException: failed to connect to dns.google/2001:4860:4860::8888 (port 443) from /2001:818:eb21:e600:e510:438c:70d1:d2e5 (port 38355) after 10000ms
        at libcore.io.IoBridge.connectErrno(IoBridge.java:185)
        at libcore.io.IoBridge.connect(IoBridge.java:130)
        at java.net.PlainSocketImpl.socketConnect(PlainSocketImpl.java:129)
        at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:356)
        at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
        at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
        at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:357)
        at java.net.Socket.connect(Socket.java:616)
        at okhttp3.internal.platform.AndroidPlatform.connectSocket

As a workaround, he tried https://firefox.dns.nextdns.io and it worked.

See also #249.