It was only a matter of time before Ben Gibbard, singer of such anthems of death and doom as “I Will Follow You Into the Dark,†“Transatlanticism,†and “We Will Become Silhouettes,†wrote a song about, well, all this. That time is today, when the Death Cab for Cutie and Postal Service bandleader — who’s been livestreaming daily performances of fan requests — released his new song, “Life in Quarantine.†“No one is going anywhere soon,†he sings in the chorus, as he describes scenes of emptiness around his home city of Seattle. “Inside the Safeway / It’s like the Eastern Bloc,†he sings of his local grocery store. “People have a way of getting crazy / When they think they’ll be dead in a month.†Gibbard will donate proceeds from the song, which he first performed in a video for Seattle alt-weekly The Stranger last week, to city organizations, including homelessness nonprofit Aurora Commons. Just try not to cry toward the end, when he sings, “I like walking beside you / Through these days of no guarantees.†Make that one guarantee: sad music for whatever we’re all going through, courtesy of Gibbard.