I've not seen this solution posted anywhere else, so here it is.
Since upgrading from Jessie Lite to Stretch Lite, I've been having problems with the first wget command after boot hanging for 45 seconds or longer before responding.
After many false leads, I found that it was due to lack of entropy to enable the handshake with an https site (github in my case). The cure was to load the rng-tools package (sudo apt-get -y install rng-tools) during my install script. The random number generator tools provide wget with enough entropy to execute the command without delay.
Dave, G8GKQ