Green’s Dictionary of Slang

(US black) any Jew, esp. the shop-owners of Harlem and other ghettos.

1965		(con. 1950s) C. Brown Manchild in the Promised Land (1969) 308: ‘Who’s Goldberg?’ ‘You know, Mr. Jew [...] Goldberg’s just as bad as Mr. Charlie. He’s got all the money in the world [...] He owns the liquor store, he owns the bar, he owns the restaurant.’.
1967		S. Katz Negro and Jew 77: So the view of ‘Goldberg’ riding around in his ‘Jew canoe,’ as a Cadillac is called by some Negroes in Los Angeles [etc.].
1980		E. Folb Runnin’ Down Some Lines 61: Goldberg and Goldstein were more or less neutral labels of identification depending on the context in which they were used.
1987		T. Wolfe Bonfire of the Vanities 5: Goldberg is the Harlem cognomen for Jew.