Why am i getting Resource temporarily unavailable [/app/Covenant.csproj] error when installing though docker

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~/Desktop/Covenant/Covenant master                                                                    
❯ sudo docker build -t covenant .                
Sending build context to Docker daemon  88.41MB
Step 1/10 : FROM mcr.microsoft.com/dotnet/core/sdk:3.1 AS build
3.1: Pulling from dotnet/core/sdk
c7c50787e2da: Pull complete 
aff359114acb: Pull complete 
821dc261e045: Pull complete 
3790459d63d5: Pull complete 
d9f67e74b01d: Pull complete 
c28a95092be1: Pull complete 
208cfb120a77: Pull complete 
Digest: sha256:150d074697d1cda38a0c2185fe43895d84b5745841e9d15c5adba29604a6e4cb
Status: Downloaded newer image for mcr.microsoft.com/dotnet/core/sdk:3.1
 ---> 1e8401d05dea
Step 2/10 : WORKDIR /app
 ---> Running in 2073026fe38c
Removing intermediate container 2073026fe38c
 ---> cdd73b7b1962
Step 3/10 : COPY . ./
 ---> aea5a30fd91e
Step 4/10 : RUN dotnet publish -c Release -o out
 ---> Running in 70f9857fe8e6
Microsoft (R) Build Engine version 16.7.3+2f374e28e for .NET
Copyright (C) Microsoft Corporation. All rights reserved.

  Determining projects to restore...
/usr/share/dotnet/sdk/3.1.426/NuGet.targets(128,5): error : Unable to load the service index for source https://api.nuget.org/v3/index.json. [/app/Covenant.csproj]
/usr/share/dotnet/sdk/3.1.426/NuGet.targets(128,5): error :   Resource temporarily unavailable [/app/Covenant.csproj]
The command '/bin/sh -c dotnet publish -c Release -o out' returned a non-zero code: 1

I get this error when i try to install using docker.
Tried using dotnet and i am getting a dotnet error, coudn't fix that so tried in docker.

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Solved this issue