title: Cannot read the data of the certain document by its ID
body: <p>I have this code:</p>
  
  <pre><code>Auth.auth().signIn(withEmail: email, password: password) { (authResult, err) in
  
  self.logInButton.isLoading = false
  
  // Check for errors
  if err != nil {
  
  // There was an error login to the system
  self.showError("Incorrect login or password")
  } else {
      let db = Firestore.firestore()
  
      guard let uid = Auth.auth().currentUser?.uid else { return }
  
      // Here the program don't enter
      // In this case, complete shows the crossed out getDocument function
      db.collection("users").document(uid).getDocument { (shapshot, error) in
      guard let snap = shapshot, error == nil else {
          self.showError(error!.localizedDescription)
          return
      }
      ...
  }
  </code></pre>
  
  <p>I can't read the data although everything exists. When a program comes to getDocument, it just doesn't go into it.  What do I do wrong? </p>
  
  <p>Upd.
  Maybe, perhaps console output will help you somehow:</p>
  
  <pre><code>2020-03-15 07:35:37.919683+0500 SmartLibrary[1956:39141] 6.19.0 - [Firebase/Analytics][I-ACS023007] Analytics v.60301000 started
  2020-03-15 07:35:37.986973+0500 SmartLibrary[1956:39141] 6.19.0 - [Firebase/Analytics][I-ACS023008] To enable debug logging set the following application argument: -FIRAnalyticsDebugEnabled (see ...)
  2020-03-15 07:35:37.992944+0500 SmartLibrary[1956:39141] 6.19.0 - [Firebase/Analytics][I-ACS031025] Analytics screen reporting is enabled. Call +[FIRAnalytics setScreenName:setScreenClass:] to set the screen name or override the default screen class name. To disable screen reporting, set the flag FirebaseScreenReportingEnabled to NO (boolean) in the Info.plist
  2020-03-15 07:35:38.412739+0500 SmartLibrary[1956:39185] 6.19.0 - [Firebase/Analytics][I-ACS800023] No pending snapshot to activate. SDK name: app_measurement
  2020-03-15 07:35:38.809486+0500 SmartLibrary[1956:39148] 6.19.0 - [Firebase/Analytics][I-ACS800003] Registered an SDK that has already registered. Default flags will be overwritten. SDK name: app_measurement
  2020-03-15 07:35:38.811448+0500 SmartLibrary[1956:39148] 6.19.0 - [Firebase/Analytics][I-ACS800023] No pending snapshot to activate. SDK name: app_measurement
  2020-03-15 07:35:39.585977+0500 SmartLibrary[1956:39134] 6.19.0 - [Firebase/Analytics][I-ACS023012] Analytics collection enabled
  </code></pre>