Build mono fail in docker alpine with Segmentation fault

Hi,

I tried to build our docker image involve mono and docker alpine. It is used to work half year ago. But yesterday when I tried to update our application code and I faced one issue.

Here is my Dockerfile

***********
```
FROM mcr.microsoft.com/dotnet/core/sdk:2.2-alpine AS dev

WORKDIR /app
RUN dotnet --version
RUN apk add --no-cache mono --allow-untrusted --repository http://dl-cdn.alpinelinux.org/alpine/edge/testing/ && \
apk add --no-cache --virtual=.build-dependencies ca-certificates && \
apk del .build-dependencies
```

***********

Here is the error:
******************
```
Building 1.0s (11/18)
=> [internal] load build definition from Dockerfile 0.0s
=> => transferring dockerfile: 1.04kB 0.0s
=> [internal] load .dockerignore 0.0s
=> => transferring context: 35B 0.0s
=> [internal] load metadata for mcr.microsoft.com/dotnet/core/runtime:2.2-alpine 0.4s
=> [internal] load metadata for mcr.microsoft.com/dotnet/core/sdk:2.2-alpine 0.4s
=> [runtime 1/3] FROM mcr.microsoft.com/dotnet/core/runtime:2.2-alpine@sha256:ed4bacf7167c3ff6f31f4d9b84e798257a 0.0s
=> [dev 1/10] FROM mcr.microsoft.com/dotnet/core/sdk:2.2-alpine@sha256:5ce9081823932f7d06ed9bf2aee6b8067e199518 0.0s
=> [internal] load build context 0.0s
=> => transferring context: 7.63kB 0.0s
=> CACHED [runtime 2/3] WORKDIR /app 0.0s
=> CACHED [dev 2/10] WORKDIR /app 0.0s
=> CACHED [dev 3/10] RUN dotnet --version 0.0s
=> ERROR [dev 4/10] RUN apk add --no-cache mono --allow-untrusted --repository http://dl-cdn.alpinelinux.org/al 0.6s
> [dev 4/10] RUN apk add --no-cache mono --allow-untrusted --repository http://dl-cdn.alpinelinux.org/alpine/edge/testing/ && apk add --no-cache --virtual=.build-dependencies ca-certificates && apk del .build-dependencies:
10 0.404 fetch http://dl-cdn.alpinelinux.org/alpine/edge/testing/x86_64/APKINDEX.tar.gz
10 0.572 Segmentation fault
executor failed running [/bin/sh -c apk add --no-cache mono --allow-untrusted --repository http://dl-cdn.alpinelinux.org/alpine/edge/testing/ && apk add --no-cache --virtual=.build-dependencies ca-certificates && apk del .build-dependencies]: exit code: 139
```
**********

I can see fetch http://dl-cdn.alpinelinux.org/alpine/edge/testing/x86_64/APKINDEX.tar.gz end up fail with Segmentation fault.

I also check the http://dl-cdn.alpinelinux.org/alpine/edge server and found this file APKINDEX.tar.gz is updated several days ago.

Is there anything I need to be aware of ?

Br, Yiqing