Fail to stack install with RedownloadHttpError

[Alendia]

Run the following code in Ubuntu 20.04 LTS with error:

$ stack install
Downloading nightly-2020-05-01 build plan ...
RedownloadHttpError (HttpExceptionRequest Request {
  host                 = "raw.githubusercontent.com"
  port                 = 443
  secure               = True
  requestHeaders       = [("User-Agent","The Haskell Stack")]
  path                 = "/fpco/stackage-nightly/master//nightly-2020-05-01.yaml"
  queryString          = ""
  method               = "GET"
  proxy                = Nothing
  rawBody              = False
  redirectCount        = 10
  responseTimeout      = ResponseTimeoutDefault
  requestVersion       = HTTP/1.1
}
 (InternalException (HostCannotConnect "127.0.0.1" [Network.Socket.connect: <socket: 11>: does not exist (Connection refused)])))

I have checked issues but cannot solve this problem and I guess it may relate to proxy settings or stack version.
I config terminal with proxy, and the settings are shown below:

export http_proxy=http://127.0.0.1:<port>
export https_proxy=http://127.0.0.1:<port>

My stack version is: 1.9.3.1 x86_64
Also, I cannot run stack update with the following error report:

$ stack update
Updating package index Hackage (mirrored at https://s3.amazonaws.com/hackage.fpcomplete.com/)                                                                                               Selected mirror https://s3.amazonaws.com/hackage.fpcomplete.com/
Updating package index Hackage (mirrored at https://s3.amazonaws.com/hackage.fpcomplete.com/)                                                                                               Downloading root
Updating package index Hackage (mirrored at https://s3.amazonaws.com/hackage.fpcomplete.com/) ...
SomeRemoteError (HttpExceptionRequest Request {
  host                 = "s3.amazonaws.com"
  port                 = 443
  secure               = True
  requestHeaders       = [("Accept-Encoding",""),("Cache-Control","no-transform"),("User-Agent","The Haskell Stack")]
  path                 = "/hackage.fpcomplete.com/root.json"
  queryString          = ""
  method               = "GET"
  proxy                = Nothing
  rawBody              = False
  redirectCount        = 10
  responseTimeout      = ResponseTimeoutDefault
  requestVersion       = HTTP/1.1
}
 (InternalException (HostCannotConnect "127.0.0.1" [Network.Socket.connect: <socket: 12>: does not exist (Connection refused)])))

[jneira]

Hi, that stack version is really old so i would suggest upgrade it.
In any case it seems a stack specific issue so maybe you could get better help in its issue tracker.
Moreover, haskell-ide-engine is in not maintained anymore as it has been superseded by haskell-language-server so i would use the latter, if possible.