Fix DNS resolution in WSL2

fix-wsl2-dns-resolution

More recent resolution:

1. cd ~/../../etc (go to etc folder in WSL).
2. echo "[network]" | sudo tee wsl.conf (Create wsl.conf file and add the first line).
3. echo "generateResolvConf = false" | sudo tee -a wsl.conf (Append wsl.conf the next line).
4. wsl -l (Get the <WSL distribution name>. Debian-XX or Ubuntu-XX (Default) etc.)
5. wsl --terminate <WSL distribution name> (Terminate WSL in Windows cmd, <WSL distribution name> from the step 4).
6. cd ~/../../etc (go to etc folder in WSL).
7. sudo rm -Rf resolv.conf (Delete the resolv.conf file).
8. In windows cmd, ps or terminal with the vpn connected do: Get-NetIPInterface or ipconfig /all for get the dns primary and
secondary. Look for Ethernet adaptor with Description "Cisco AnyConnect...". From under it take values for DNS Servers. 
It has primary and secondary DNS server IPs.
9. Use commands in next two steps by replacing X.X.X.X for values of Primary and Secondary DNS server IPs respectively 
10. echo "nameserver X.X.X.X" | sudo tee resolv.conf (Create resolv.conf and append the line.)
11. echo "nameserver X.X.X.X" | sudo tee -a resolv.conf (Append the line in resolv.conf)
12. wsl --terminate <WSL distribution name> (Terminate WSL in Windows cmd, <WSL distribution name> from the step 4).
13. sudo chattr +i resolv.conf
14. And finally in windows cmd, ps or terminal:
Get-NetAdapter | Where-Object {$_.InterfaceDescription -Match "Cisco AnyConnect"} | Set-NetIPInterface -InterfaceMetric 6000

Credit: @MartinCaccia, @yukosgiti, @machuu and @AlbesK:
https://github.com/microsoft/WSL/issues/4277
https://github.com/microsoft/WSL/issues/4246

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Original resoltuion:

1. Create a file: /etc/wsl.conf.
2. Put the following lines in the file in order to ensure the your DNS changes do not get blown away

[network]
generateResolvConf = false

3. In a cmd window, run wsl --shutdown
4. Restart WSL2
5. Create a file: /etc/resolv.conf. If it exists, replace existing one with this new file.
6. Put the following line in the file

nameserver 8.8.8.8 # Or use your DNS server instead of 8.8.8.8 which is a Google DNS server

7. Repeat step 3 and 4. You will see git working fine now.

Credit: https://github.com/microsoft/WSL/issues/4285#issuecomment-522201021