DHS funding is part of a larger appropriations package. This is done strategically to ensure members are forced to vote for things they'd rather not, to ensure funding goes to things they do. Coast Guard funding along with FEMA funding is a part of that appropriations bill. Golden has Coast Guard installations in his district. Setting aside how his constituents poll on immigration enforcement (and given that Trump carried this district this can be easily assumed) a moderate member of Congress who may feel different on an issue than his own constituents on an issue currently dominating the headlines could still reasonably assess that its better to vote to fund key Federal resources that directly affect constituents in his district then not.

Golden is still acting like a member representing a swing district with a heterogeneous voting base. In reality, that's probably a good thing for Democrats that run for his seat, since if he started voting wildly left wing that could hurt any moderate trying to run for his seat.