dlopen_derive hasn't been updated since June 9, 2019.
dlopen_derive depends on quote = "0.6.12" and syn = "0.15.34". Versions 1.0.0 of these dependencies were published on August 13, 2019. The 0.* versions haven't received updates since.
Note that dlopen is an unmaintained crate from the same repository as dlopen_derive. However, migrating away from dlopen_derive implies migrating away from dlopen, as well.
dlopen2_derive (and dlopen2){
"license": "CC0-1.0"
}