Update 01-Develop-Entity-Services.md

[ozboms]

tried to make it a little clearer based on my understanding (but if this changes the definition, feel free to lmk and I'll change it back)

[ozboms]

In the songs sample, we currently can just do songs[id] because the index happens to match the id; the sample should actually use a for loop just in case there are new songs that don't match the number index.

var data song // if the ids don't match the index for i := range songs { if songs[i].Id == reqIdInt { data = songs[i] } }

[ozboms]

add comments from code to pull request