cl-user> (quick-update)
The most up-to-date client, version 2017-03-06, is already installed.
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You already have the latest version of "quicklisp": 2018-07-11.
nil
cl-user> (ql:quickload :cl-ftp)
(defpackage :example
  (:use :cl
        :ftp))
(in-package :example)

; Works
(with-ftp-connection (conn :hostname "ftp.ncdc.noaa.gov" :passive-ftp-p t)
  (retrieve-file "pub/data/noaa/readme.txt" "./readme.txt"))

; Does not work - I am expecting an ftp:ftp-error in this case but instead it hangs forever
(with-ftp-connection (conn :hostname "ftp.ncdc.noaa.gov" :passive-ftp-p t)
  (retrieve-file "pub/data/noaa/fake-file-does-not-exist.txt" "./file.txt"))
To load "cl-ftp":
  Load 1 ASDF system:
    cl-ftp
; Loading "cl-ftp"

;Compiler warnings :
;   In an anonymous lambda form: In the call to retrieve-file with arguments ("pub/data/noaa/readme.txt" "./readme.txt"),
;     2 arguments were provided, but at least 3 are required
;     by the current global definition of retrieve-file
; Evaluation aborted on #<ccl:no-applicable-method-exists #x302372F1BE9D>.
example>