fix race with getStore() (#45)

by calling it once before starting the server

closes: #44

src/Main.hs

@@ -341,6 +341,8 @@ main = do
     options@Options{ priority, timeout, verbosity } <- do
         Options.execParser Options.parserInfo
 
+    Nix.initStore
+
     storeDirectory <- Nix.getStoreDir
 
     secretKeyFile <- Environment.lookupEnv "NIX_SECRET_KEY_FILE"

src/Nix.hsc

@@ -34,6 +34,8 @@ import qualified Foreign
 
 #include "nix.hh"
 
+foreign import ccall "initStore" initStore :: IO ()
+
 foreign import ccall "freeString" freeString :: Ptr String_ -> IO ()
 
 data String_ = String_ { data_ :: Ptr CChar, size  :: CSize }