use default image

Dockerfile

-FROM mono:5.20.1.34 as sqlite-builder
+FROM debian:buster-slim as sqlite-builder
 
 RUN apt-get update && \
-	apt-get -y install wget sqlite3 libsqlite3-dev p7zip-full && \
+	apt-get -y install wget sqlite3 libsqlite3-dev p7zip-full mono-complete && \
 	rm -rf /var/lib/apt/lists/*
 WORKDIR /
 RUN wget https://minio.mycard.moe:9000/nanahira/sqlite-netFx-full-source-1.0.112.0.zip && \
@@ -9,17 +9,21 @@ RUN wget https://minio.mycard.moe:9000/nanahira/sqlite-netFx-full-source-1.0.112
 	cd sqlite && \
 	xbuild /p:Configuration=Release /p:UseInteropDll=false /p:UseSqliteStandard=true ./System.Data.SQLite/System.Data.SQLite.2015.csproj
 
-FROM mono:5.20.1.34 as builder
+FROM debian:buster-slim as builder
+
+RUN apt-get update && \
+	apt-get -y install mono-complete && \
+	rm -rf /var/lib/apt/lists/*
 
 COPY . /ImgGen
 WORKDIR /ImgGen
 COPY --from=sqlite-builder /sqlite/bin/2015/ReleaseMonoOnPosix/bin/System.Data.SQLite.dll .
 RUN xbuild /p:Configuration=Release /p:TargetFrameworkVersion=v4.6
 
-FROM mono:5.20.1.34
+FROM debian:buster-slim
 
 RUN apt-get update && \
-	apt-get -y install xfonts-utils fontconfig wget p7zip-full && \
+	apt-get -y install xfonts-utils fontconfig wget p7zip-full mono-complete && \
 	rm -rf /var/lib/apt/lists/*
 
 WORKDIR /